Display device having embedded touch screen and method for detecting touch

ABSTRACT

Disclosed herein are a display device having an embedded touch screen and a method for detecting a touch, and more particularly, a display device having an embedded touch screen capable of preventing deterioration of image quality generated in the display device when a touch sensor and a sensor signal line are disposed in the display device and solving a problem that sensitivity of a detected touch signal is weakened due to a parasitic capacitance generated between the touch sensor and the sensor signal line and a signal line and components of the display device, and a method for detecting a touch.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from and the benefit of Korean PatentApplication No. 10-2015-0176960, filed on Dec. 11, 2015, which is herebyincorporated by reference for all purposes as if fully set forth herein.

BACKGROUND

Field

The present disclosure relates to a display device having an embeddedtouch screen and a method for detecting a touch.

Discussion of the Background

Generally, a touch screen, which is an input device added on displaydevices such as a liquid crystal display (LCD), a plasma display panel(PDP), an organic light emitting diode (OLED), an active matrix organiclight emitting diode (AMOLED), and the like, or embedded in the displaydevice, is a device recognizing an object such as a finger, a touch pen,or the like, contacting the touch screen as an input signal. A touchinput device has been recently mounted mainly in mobile apparatuses suchas a mobile phone, a personal digital assistants (PDA), a portablemultimedia player (PMP), and the like, and has also been used in allindustrial fields such as a navigation device, a netbook computer, alaptop computer, a digital information device, a desktop computersupplying a touch input supporting operating system, an Internetprotocol television (IPTV), a state-of-the-art fighter, a tank, anarmored motorcar, and the like.

A display device in which the touch screen described above is used maybe divided into a touch screen add-on type display device, a touchscreen on-cell type display device, and a touch screen in-cell typedisplay device depending on a structure thereof. The touch screen add-ontype display device is manufactured by individually manufacturing adisplay device and a touch screen and then adding the touch screen on anupper plate of the display device, has a thick thickness, and has lowbrightness to have low visibility. The touch screen on-cell type displaydevice is manufactured by directly forming elements constituting a touchscreen on an upper substrate of a display device (a color filter of anLCD or a sealing substrate of an OLDE), and may have a thickness reducedas compared with the touch screen add-on type display device, but maynot be manufactured in an existing process of manufacturing an LCD, suchthat additional equipment investment is required or a manufacturing costis increased at the time of manufacturing the touch screen on-cell typedisplay device using an existing equipment.

On the other hand, the touch screen in-cell type display device may bemanufactured without an additional investment in equipment in a processof manufacturing a display device such as an LCD, an OLED, or the like,such that a manufacturing cost is reduced, and a high performancedisplay device manufacturing equipment may be used. Therefore, a yieldis increased, such that the manufacturing cost is further reduced.

However, in the touch screen in-cell type display device according tothe related art, touch sensors and sensor signals lines generateinterference with driving signal lines of the display device to causedeterioration of image quality of the display device, such that thetouch sensors and the sensor signal lines are viewed, and in the case inwhich the sensor signal lines are disconnected, performance of the touchscreen is deteriorated.

In addition, in the case in which the touch screen is embedded in theLCD, when pixel electrodes or source lines or gate lines of the LCD andthe touch sensors or the sensor signal lines overlap with each other ina vertical or horizontal direction, a physical parasitic capacitance isgenerated, and a magnitude of the parasitic capacitance is significantlylarge, such that due to the parasitic capacitance, touch sensitivity isdeteriorated or touch signals may not be detected in an extreme case.

BRIEF SUMMARY OF THE INVENTION

The present invention has been suggested in order to solve the problemsin the related art as described above, and an object of the presentinvention is to form a touch sensor and a sensor signal line so as to bepositioned above or below (or on the same line as) a driving signal line(a source line, a gate line, or the like) of a display device to preventa signal line from being observed in the display device and remove aninfluence of the touch sensor and the sensor signal line on the displaydevice, thereby preventing a malfunction of the display device.

According to an exemplary embodiment of the present invention, a displaydevice having an embedded touch screen is provided, the display devicecomprising: a substrate on which pixel electrodes and driving signallines are disposed, wherein a sensor layer on which touch sensors andsensor signal lines are disposed is formed above or below the drivingsignal lines, a guard layer is formed between the driving signal linesand the sensor layer, and the guard layer is applied with a firstvoltage and a second voltage which are different from each other.

The guard layer is divided to be overlapped with the touch sensors in aone-to-one scheme.

The guard layer overlapped with a first touch sensor detecting a touchis applied with the first voltage applied to the first touch sensor, andthe guard layer overlapped with a second touch sensor that does notdetect the touch is applied with the second voltage applied to thesecond touch sensor.

The first voltage is an alternating voltage applied to a first touchsensor detecting a touch.

The first voltage is a precharge voltage applied to a first touch sensordetecting a touch.

the second voltage is a direct current (DC) voltage or a ground voltageapplied to a second touch sensor that does not detect a touch.

The first voltage and the second voltage are supplied from a touch driveIC.

The touch drive IC is integrated with a display drive IC.

The touch drive IC detects a touch based on an alternating voltage,which is the first voltage.

The first voltage and the second voltage are supplied from a powermanagement IC.

According to another exemplary embodiment of the present invention, Amethod for detecting a touch of a display device having an embeddedtouch screen including a substrate on which pixel electrodes and drivingsignal lines are disposed, the method comprising: forming a sensor layeron which touch sensors and sensor signal lines are disposed, above orbelow the driving signal lines, forming a guard layer between thedriving signal lines and the sensor layer, and applying the guard layerwith a first voltage and a second voltage which are different from eachother.

The guard layer is divided to be overlapped with the touch sensors in aone-to-one scheme.

In the applying the guard layer with the first voltage and the secondvoltage, the guard layer overlapped with a first touch sensor detectinga touch is applied with the first voltage applied to the first touchsensor, and the guard layer overlapped with a second touch sensor thatdoes not detect the touch is applied with the second voltage applied tothe second touch sensor.

The first voltage is an alternating voltage applied to a first touchsensor detecting a touch.

The first voltage is a precharge voltage applied to a first touch sensordetecting a touch.

The second voltage is a direct current (DC) voltage or a ground voltageapplied to a second touch sensor that does not detect a touch.

The first voltage and the second voltage are supplied from a touch driveIC.

The touch drive IC is integrated with a display drive IC.

The touch drive IC detects a touch based on an alternating voltage,which is the first voltage.

The first voltage and the second voltage are supplied from a powermanagement IC.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual diagram of a three-terminal switching elementaccording to an exemplary embodiment of the present invention.

FIG. 2 is a view for describing a principle in which a touch capacitanceand a capacitance between lines are formed.

FIG. 3 is a circuit diagram illustrating a basic structure of a touchdetecting means in the display device having an embedded touch screenaccording to an exemplary embodiment of the present invention.

FIG. 4 is an equivalent circuit diagram of FIG. 3.

FIG. 5 is a view illustrating an example in which a touch sensoraccording to an exemplary embodiment of the present invention applies analternating voltage to an equivalent capacitor Ceq between lines inorder to detect a touch signal.

FIG. 6 is a view illustrating a structure of an LCD.

FIG. 7 is a view illustrating a detailed structure of a thin filmtransistor (TFT) of FIG. 6.

FIG. 8 is a structure view of a display device having an embedded touchscreen according to a first exemplary embodiment of the presentinvention.

FIG. 9 is a view illustrating an example of a layout of touch sensorsand a touch integrated circuit (IC) in the display device having anembedded touch screen according to an exemplary embodiment of thepresent invention.

FIG. 10 is a view illustrating a configuration of touch sensors in thedisplay device having an embedded touch screen according to an exemplaryembodiment of the present invention.

FIG. 11 is a structure view of the display device having an embeddedtouch screen according to a second exemplary embodiment of the presentinvention.

FIG. 12 is a view illustrating the use of a guard layer (G/L) and atransfer of a driving signal according to an exemplary embodiment of thepresent invention.

FIGS. 13 to 15 are views illustrating a concept in which an AC inputvoltage is applied, in a method for detecting a touch of a displaydevice having an embedded touch screen according to an exemplaryembodiment of the present invention.

FIG. 16 is a view for describing a method of applying required signalsto a display device, a touch sensor, and a G/L in the display devicehaving an embedded touch screen according to an exemplary embodiment ofthe present invention.

FIG. 17 is a structure view of the display device having an embeddedtouch screen according to a third exemplary embodiment of the presentinvention.

FIG. 18 is a structure view of the display device having an embeddedtouch screen according to a fourth exemplary embodiment of the presentinvention.

FIG. 19 is a view illustrating a configuration of a TFT substrate amongcomponents of an LCD using a transversal electric field mode.

FIG. 20 is a view illustrating an example of a display device having anembedded touch sensor according to an exemplary embodiment of thepresent invention using a Vcom electrode in a transversal electric fieldmode.

FIG. 21 illustrates a method for detecting a touch signal using a commonelectrode of the display device having an embedded touch screenaccording to an exemplary embodiment of the present invention thattogether performs a function of a touch sensor as the common electrode.

FIG. 22 is a conceptual view illustrating a case in which the touchsensor does not sense a vertical or horizontal motion of an object.

FIGS. 23A and 23B illustrate examples about a sharing of a touch sensorarea according to an exemplary embodiment of the present invention,where the area is shared in a longitudinal direction.

FIG. 24 illustrates an example about a sharing of a touch sensor areaaccording to an exemplary embodiment of the present invention, where thearea is shared in a transversal direction.

FIG. 25 is a view of an example in which up and down or left and rightareas of the touch sensors are shared in a case in which the touchsensors are positioned on upper surfaces or lower surfaces of gate linesor source lines according to an exemplary embodiment of the presentinvention.

FIG. 26 illustrates an example of a sharing of the touch sensor area ina case in which the common electrodes act as the touch sensors.

FIG. 27 illustrates a structure of an IC in which an LDI and a TDI areintegrated into one IC according to an exemplary embodiment of thepresent invention.

FIGS. 28 to 30 are views illustrating a layout concept of the commonelectrodes and the sensor signal lines when the common electrodes act asthe touch sensors, according to an exemplary embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Hereinafter, exemplary embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.

First, the present invention relates to a display device having anembedded touch screen and a method for detecting a touch, and moreparticularly, to a method of detecting a touch by applying a drivingvoltage to a driving capacitor (Cdrv) in a touch integrated circuit (IC)when a capacitance by a touch of a finger, or the like, is applied to asensing pad (a pad connected to a touch detecting unit) or detecting atouch using a phenomenon that a difference in a detection voltage due toa magnitude difference in a capacitance caused by the touch is generatedwhen an alternating driving voltage is applied to a sensing equivalentcapacitor formed between the sensing pad (the pad connected to the touchsensing unit) that is detecting the touch and a non-sensing pad (a padthat corresponds to the sensing pad and is not connected to the touchdetecting unit), and a touch structure in a display device enabling thedetection of the touch. In the method of detecting a touch according toan exemplary embodiment of the present invention, magnitudes of avoltage detected when a touch is not generated and a voltage detectedwhen a touch capacitance is applied by generation of a touch arecompared with each other, the touch is detected by a difference betweenthe magnitudes of these two voltages, and an influence by a parasiticcapacitance, or the like, is minimized by a guard layer (G/L), therebymaking it possible to more stably obtain a touch signal.

A display device stated in the present invention is any one of a kind ofliquid crystal display (LCD), a plasma display panel (PDP), an activematrix organic light emitting diode (AMOLED), and a passive matrixorganic light emitting diode (PMOLED), or includes all means displayingany type of still image (such as JPG, TIF, or the like) or movingpicture (MPEG-2, MPEG-4, or the like) to users.

A touch input means in the present invention includes any type of input(for example, an object such as a conductor having a predetermined formor an input such as an electromagnetic wave, or the like) generating avoltage change that may be sensed by a touch sensor, as well as akeyboard, a mouse, a finger, a touch pen, and a stylus pen.

In addition, in the present disclosure, a phrase “on the same line” isused as the meaning that two components overlap with each other at thesame position in a vertical direction, and a metal material, aninsulator, or the like, forming a signal line may be present between thetwo components. For example, when A and B are positioned on the sameline, it means that A is positioned on an upper surface of B or B or ispositioned on an upper surface of A, and another material such as aninsulator, a metal, or the like, may be present between A and B. When Aand B are positioned on the same line, a width of A and a width of B arenot limited unless separately mentioned, and a ratio between the widthsof A and B is not specified unless separately mentioned. However, in thepresent disclosure, it is considered that the width of A and the widthof B are the same as each other by way of example.

In addition, components such as ˜ units to be described below areassemblies of unit function elements performing specific functions. Forexample, an amplifier of a certain signal is a unit function element,and an assembly in which the amplifier and signal converters arecollected may be called a signal converting unit. In addition, a ˜ unitmay be included in a larger component or ˜ unit or may include smallercomponents or ˜ units. In addition, a ˜ unit may include an individualcentral processing unit (CPU) that may process calculation functions orcommands, or the like, stored in a memory, or the like.

In the following drawings, thicknesses or areas are exaggerated in orderto clearly represent several layers and areas. Throughout the presentdisclosure, similar components will be denoted by like referencenumerals. When a portion such as a layer, a area, a substrate, or thelike, is referred to as being positioned on an upper portion of anotherportion, a portion may be directly positioned on another portion (theother portion is not present therebetween) or the other portion (forexample, a medium layer or an insulating layer) may be presenttherebetween.

In addition, a “signal” stated in the present disclosure generallyindicates a voltage or a current unless specifically mentioned.

In addition, in the present disclosure, a capacitance indicates aphysical magnitude. Meanwhile, a “capacitor” indicates an element havinga capacitance, which is a physical magnitude. In the present invention,a compensation capacitor (Cbal) is formed in a touch drive IC by adesign and manufacturing process or is naturally formed between adjacenttwo sensor signal lines. In the present disclosure, both of the directlyformed capacitor and the naturally formed capacitor will be called a“capacitor” without being distinguished from each other.

In the present disclosure, C used as a sign of a capacitor is used as asign indicating the capacitor, and also indicates a capacitance, whichis a magnitude of the capacitor. For example, C1 is not only a signindicating a capacitor, but also indicates a capacitance of thecapacitor.

In addition, in the present disclosure a phrase “applying a signal”means that a level of a signal maintained in a certain state is changed.For example, a phrase “applying a signal to an on/off control terminalof a switching element” means that an existing low level voltage (forexample, a zero Volt or a direct current (DC) voltage or an AC voltagehaving a predetermined magnitude) is changed into a high level (forexample, a DC voltage or an AC voltage having an amplitude value largerthan that of the low level voltage).

In addition, in the present disclosure, touch sensors indicates sensingpads that are performing sensing and non-sensing pads. The sensing padsare touch sensors connected to touch detecting units in order to detecta touch among a plurality of touch sensors, and the non-sensing pads aretouch sensors that do not perform detection of a touch and are notconnected to the touch detecting unit. The sensing pads become thenon-sensing pads after detection of a touch is completed, and anynon-sensing pads are changed into sensing pads depending on apredetermined sequence. Therefore, the sensing pads and the non-sensingpads are not fixed, but may be changed depending on a time, and changesequences of the respective sensing pads and non-sensing pads may besequentially determined depending on a predetermined sequence. A timesharing technology is an example of determining a sequence.

In addition, in the present disclosure, a phrase “detecting a touch” hasthe same meaning as that a phrase “detecting a touch signal”, and atypical example of detection of a touch signal is to detect a differencebetween a first voltage detected by a touch detecting unit when aconductor such as a finger does not touch or approach a touch sensor,such that a touch capacitance is not formed, and a second voltagedetected by a touch detecting unit by a touch capacitance (Ct) formedwhen the conductor such as the finger overlaps with the touch sensor.

In addition, in the present disclosure, a touch driver IC will becontracted as a touch IC or a TDI.

Further, in the present disclosure, pre-charging and charging and apre-charging voltage and a charging voltage will be used as the samemeaning.

Further, in the present disclosure, sensing pads may include sensorsignal lines connecting the sensing pads to each other unlessspecifically mentioned, and non-sensing pads may include non-sensing padsignal lines connecting the non-sensing pads to each other unlessspecifically mentioned.

Further, in the present disclosure, source lines and gate lines will becalled signal lines, and the signal lines generally indicate the gateline and the source lines or indicate only the source line or only thegate lines.

Further, in the present disclosure, a sub-pixel will also be called apixel.

FIG. 1 is a conceptual diagram of a three-terminal switching elementused as an example of a capacitor charging means in an exemplaryembodiment of the present invention among switching elements. Referringto FIG. 1, the three-terminal switching element generally includes threeterminals such as an on/off control terminal Cont, an input terminal In,and an output terminal Out. The on/off control terminal Cont is aterminal controlling a turn-on/turn-off of the switching element, andwhen a voltage or a current having a predetermined magnitude is appliedto the off control terminal Cont, a voltage or a current applied to theinput terminal In is output in a voltage or current form to the outputterminal Out.

Before describing an example of a method for detecting a touch signalaccording to an exemplary embodiment of the present invention in detail,a principle in which a touch capacitance and a capacitance between linesis formed will be described with reference to FIG. 2. In an example ofFIG. 2, it is assumed that a touch sensor 10 and a finger 25 are spacedapart from each other by an interval of “d” and have an overlap area (oran overlap contact area) of “A” when the finger 25 or a conductive touchmeans (for example, a capacitive touch pen) similar to the finger 25approaches the touch sensor 10. In this case, as represented by a rightequivalent circuit and Equation: “C=(eA)/d” of FIG. 22, a capacitance“C” is formed between the finger 25 and the touch sensor 10. In thepresent disclosure, the capacitance formed between the finger 25 and thetouch sensor 10 is called a touch capacitance Ct.

In addition, in the example of FIG. 2, when two sensor signal linesparallel with each other, instead of the finger 25 and the touch sensor10, are spaced apart from each other by an interval of “d” and have anoverlap area of “A”, a capacitance C between lines as represented by anequivalent circuit and Equation: “C=(eA)/d” of FIG. 2 is also formedbetween the two sensor signal lines. When the signal lines are formed ofITO or a metal, a value obtained by multiplying a thickness of anapplied ITO or metal by overlap lengths between the two signal linesbecomes an overlap area between the two signal lines parallel with eachother, and a level at which the two overlapping signal lines are spacedapart from each other becomes a spaced distance. In an exemplaryembodiment of the present invention, since an optically clear adhesiveor an air layer is formed between the two signal lines, permittivity ofthe OCA or the air may be used as permittivity (e) in Equation:“C=(eA)/d” of FIG. 2.

FIG. 3 is a circuit diagram illustrating a basic structure of a touchdetecting means in the display device having an embedded touch screenaccording to an exemplary embodiment of the present invention. Referringto FIG. 3, the touch detecting means specialized according to anexemplary embodiment of the present invention has a basic structureincluding a charging means 12, touch sensors 10, sensor signal lines 22,a parasitic capacitance capacitor Cp, and a touch detecting unit 14.

The charging means 12 is a switching element such as a transistor (TR),a field effect transistor (FET), a metal oxide semiconductor FET(MOSFET), a complementary metal oxide semiconductor (CMOS), or the like,supplying Vpre, which is a pre-charging signal (or a charging signal),to all capacitors connected to the touch detecting unit 14 and turnedoff by a turn-off signal applied to an “on-off control terminal” called“Cont” to make an output terminal 12-1 a high impedance state or alinear element such as an operational amplifier (OPAMP) supplying asignal depending on a control signal.

The touch sensors 10 include sensing pads 10 a that are connected to thetouch detecting unit 14 and detect a touch signal and non-sensing pads10 b that are not connected to the touch detecting unit 14 and do notdetect a touch signal.

The sensing pads 10 a and the non-sensing pads 10 b are not fixed, andthe same touch sensors 10 may be changed by a time sharing technology(the sensing pads are changed into the non-sensing pads after apredetermined time interval. The sensing pads 10 a are connected to thetouch detecting unit 14 in order to detect a touch, and the non-sensingpads 10 b are not connected to (or are spaced apart from) the touchdetecting unit 14. Therefore, one touch sensor 10 is divided into thesensing pad and the non-sensing pad depending on whether or not to beconnected to the touch detecting unit 14.

It is assumed in an example of FIG. 3 that the touch sensors 10 becomethe sensing pad one by one and the other touch sensors 10 are thenon-sensing pads, and a touch sensor 10 denoted by “PC” is operated asthe sensing pad 10 a, and all of the other touch sensors are thenon-sensing pads PA, PB, PD, PE, PF, PG, PH, PI, and PJ. The touchsensor denoted by “PB” serves as the sensing pad before the sensing pad10 a denoted by “PC” is operated, and the touch sensor denoted by “PD”is changed from the non-sensing pad into the sensing pad after thesensing pad denoted by “PC” is operated. As described above, the changeof the touch sensor 10 into the sensing pad and the non-sensing pad isperformed by a control of a timing controlling unit 33 of FIG. 9. FIG. 3illustrates an example of a method of detecting a touch signal using onesensing pad 10 a, and a plurality of touch sensors may be simultaneouslyoperated as sensing pads.

In FIG. 3, when the pre-charging voltage Vpre is applied to a sensingpad signal line 22 a and the sensing pad 10 a denoted by PC, andnon-sensing pads adjacent to the sensing pad 10 a and denoted by PB, PD,and PF and non-sensing signal pad lines 22 b-B, 22 b-D, and 22 b-Fconnected to the non-sensing pads are connected to any voltage Vlblhaving a predetermined potential difference from Vpre, capacitance areformed between the sensing pad 10 a and the non-sensing pads 10 b by theprinciple described with reference to FIG. 2.

In detail, since Vpre having a predetermined potential is applied to thesensing pad signal line 22 a and the sensing pad 10 a and thenon-sensing pad signal line 22 b-B connected to Vlbl has a predeterminedoverlap distance and overlap area with respect to the sensing pad signalline 22 a, a capacitance between lines corresponding to C1 is formedbetween the sensing pad signal line 22 a and the non-sensing pad signalline 22 b-B by the principle described with reference to FIG. 2, acapacitance between lines corresponding to C2 is formed between thesensing pad signal line 22 a and the non-sensing pad signal line 22 b-Dby the same principle, and a capacitance between lines corresponding toC3 is formed between the sensing pad (PC) 10 a and the non-sensing padsignal line 22 b-F overlapping with the sensing pad 10 a by the sameprinciple.

In the related art, this capacitance between lines acts as a parasiticcapacitor (Cp) to act as noise reducing touch sensitivity. However, inan exemplary embodiment of the present invention, since the capacitancebetween lines is inversely used to detect the touch signal, Cp inEquation for calculating a voltage detected in the touch detecting unitis reduced to improve touch sensitivity, and the capacitance betweenlines, which is the reduced Cp, is disposed at a numerator position ofEquation for the voltage detected in the touch detecting unit to improvetouch sensitivity, thereby doubly improving the touch sensitivity.

Meanwhile, even though the non-sensing pad signal line 22 b-B is presentbetween the sensing pad signal line 22 a and the non-sensing pad signalline 22 b-A, a capacitance C4 between lines may be formed In the presentdisclosure, capacitances between lines such as C1 to C3 formed betweenthe sensing pad signal line 22 a and the non-sensing pad signal linesare defined as primary capacitances between lines, and capacitances suchas C4 formed in a state in which one non-sensing pad signal line ispresent or a plurality of non-sensing pad signal lines are presentbetween the sensing pad signal line 22 a and a non-sensing pad signalline are defined as secondary capacitances between lines.

Therefore, a plurality of secondary capacitances between lines may beformed in the sensing pad 10 a and the sensing pad signal line 22 a.Since the touch sensitivity is improve when the secondary capacitancesbetween lines are used to detect the touch, it is preferable to connectall of the non-sensing pad signal lines for forming the secondarycapacitances between lines to Vlbl used to form the primary capacitancesbetween lines. The non-sensing pad signal lines for forming thesecondary capacitances between lines may be connected to a potentialdifferent Vlbl, but it is preferable to commonly use Vlbl in order tosimplify a circuit.

In order to simplify the circuit or weaken the touch sensitivity in thecase in which the touch sensitivity is excessively better than anexpected value, it is possible to maintain the non-sensing pad signallines (the non-sensing pad signal lines 22 b-A and 22 b-E in an exampleof FIG. 3) for forming the secondary capacitances between lines in afloating or high impedance state. Therefore, the secondary capacitancesbetween lines are not generated between the floated non-sensing padsignal lines and the sensing pad signal line. A touch driver IC (TDI)has a means generating the secondary capacitances between lines anddetermining whether to connect the non-sensing pad signal line 22 badjacent to the sensing pad signal line 22 a to a predeterminedpotential or maintain the non-sensing pad signal line 22 b adjacent tothe sensing pad signal line 22 a in the floating or high impedancestate. The voltage Vlbl connected to the non-sensing pad signal line 22b is a DC potential or an AC voltage including zero (0) V.

Since the primary capacitances C1 to C3 between lines and the secondarycapacitances between lines are commonly connected to the sensing pad 10a, all of them may be represented by one equivalent capacitor. When oneequivalent capacitor is an equivalent capacitor Ceq between lines, thecircuit of FIG. 3 may be represented by an equivalent circuit asillustrated in FIG. 4.

Meanwhile, the equivalent capacitor Ceq between lines has the followingfeatures.

1. As an overlap length between the sensor signal lines 22 a and 22 boverlapping with each other becomes long, an overlap area becomes wide,such that an equivalent capacitance Ceq between lines becomes large.Therefore, as the sending pads 10 a become distant from the TDI,equivalent capacitances Ceq between lines become large.

2. It is possible to adjust a magnitude of the equivalent capacitanceCeq between lines depending on an overlap distance between the sensorsignal lines 22 a and 22 b overlapping with each other. Since theoverlap distance is a width between the sensor signal lines 22 a and 22b overlapping with each other, it is possible to change the magnitude ofthe equivalent capacitance Ceq between lines by a design.

Referring to FIG. 4, the equivalent capacitor Ceq between lines isformed between the sensing pad 10 a and the non-sensing pad 10 badjacent to the sensing pad 10 a, and the non-sensing pad 10 b isconnected to any voltage Vlbl.

A plurality of non-sensing pads and non-sensing pad signal lines formingthe primary capacitances between lines and the secondary capacitancesbetween lines in FIG. 3 are represented by one equivalent non-sensingpad 10 b and one equivalent non-sensing pad signal line 22 b. Since thepredetermined voltage Vlbl is connected to all of the non-sensing padsignal lines 22 b except for the sensing pad 10 a in FIG. 3, the voltageVlbl is also connected to the non-sensing pad signal line 22 b in FIG.4.

Therefore, although FIG. 4 illustrates as if the voltage Vlbl isconnected to one non-sensing pad signal line 22 b, Vlbl is actuallyconnected to the plurality of non-sensing pad signal lines generatingthe primary and secondary capacitances between lines.

Vlbl, which is a voltage applied to one side of the non-sensing padsignal line 22 b when the pre-charging voltage Vpre is applied to thesensing pad, is a voltage for forming the equivalent capacitance Ceqbetween lines by pre-charging. An alternating voltage is applied to thenon-sensing pad signal line 22 b in order to detect the touch signal,and Vlbl includes a low voltage or a high voltage of the alternatingvoltage.

An output terminal 12-1 of the charging means 12 and all the capacitorsconnected to the output terminal 12-1 are connected to the touchdetecting unit 14. A buffer 14-1 is one of components constituting thetouch detecting unit 14, and an input terminal of the buffer has highimpedance (hereinafter, referred to as Hi-z) characteristics. When theoutput terminal 12-1 of the charging means 12 is connected to a Hi-zinput terminal of the touch detecting unit in a Hi-z state, all thecapacitor Ceq, Ct, Cvcom, and Cp connected between the output terminal12-1 of the charging means 12 and the buffer 14-1 become a Hi-z state.

As described below, a magnitude of Ceq is changed depending on a lengthof the sensing pad signal line 22 a connecting the sensing pad 10 a, andthus, a charging time is also changed depending on a position of thesensing pad. Since the charging time cannot but be determined to be thelongest charging time when the charging time is determined to be onefixed time, a touch detection time becomes slow. Therefore, the TDI hasa means that may determine the charging time. The charging time isdetermined to be a turn-on time of the charging means 12.

Although a case in which the output terminal 12-1 of the charging means12 is directly connected to the buffer 14-1 has been illustrated by wayof example in FIG. 4, all the elements of which inputs are in a Hi-zstate, such as a gate of a MOS, a gate of a TFT, or the like may be usedinstead of the buffer 14-1. The reason why the output terminal 12-1 ofthe charging means 12 and the touch detecting unit 14 become the Hi-zstate is that a discharging route of isolated electric charges is notpresent in the Hi-z state, such that it is easy to detect a relativelyaccurate magnitude of a variation because the magnitude of the voltageformed at a point P of FIG. 4 is maintained for a long time.

A signal output from the buffer 14-1 is input to an amplifier 14-2. Inthe case in which a change amount in the voltage detected at the point Pof FIG. 4 depending on whether or the touch is generated is small, it ispreferable to amplify the signal using the amplifier 14-2. A DAC 14-3may be used in the amplifier, and is generated using a ref voltage 14-4.

In addition, the signal detected and amplified in the touch detectingunit 14 may pass through an ADC 14-5 to be transferred to a signalprocessing unit 35 of FIG. 9. One ADC 14-5 or a plurality of ADCs 14-5may be used, and when the plurality of ADCs 14-5 are used, the signalmay be more rapidly processed.

Structures of the touch sensors in the display device having an embeddedtouch sensor according to an exemplary embodiment of the presentinvention are the same as those of the touch sensors described above,and the sensor signal lines 22 connecting the touch sensors are signallines connecting polarity of touch capacitances formed when a touchmeans such as the finger 25 approaches the touch sensors 10 to the touchdetecting unit 14, and may be formed using the same mask as the maskused to form the touch sensors 10. Referring to FIG. 4, a magnitude of aresistance of the sensor signal line 22 is denoted by Rt, and amagnitude of a resistance of the non-sensing pad 10 b is denoted by Rnt.

Since these resistance components act as factors generating a delay ofthe touch signal at the time of detecting the touch signal, it ispreferable that they are small. Therefore, it is preferable that thenumber of connections of the sensor signal signals 22 connected to thetouch sensors disposed at a distance distant from the TDI is increasedin order to reduce a resistance.

Again referring to FIG. 4, when the finger 25 of a human body approachesthe touch sensor 10 at a predetermined interval, a touch capacitance Ctis formed between the finger 25 and the touch sensor 10. Ct, which is avalue set by Equation: C=(eA)/d of FIG. 2, may be adjusted by adjustingan interval, an overlap area, or the like, between the touch means suchas the finger 25 and the touch sensor 10. For example, when an area ofthe touch sensor 10 is increased, Ct is also increased depending onEquation of FIG. 2. To the contrary, when an area of the touch sensor 10is reduced, Ct is also reduced. As an example, Ct may be designed to beseveral femto Farad (fF) to several tens of micro F.

Again referring to FIG. 4, the pre-charging voltage Vpre is applied toan input terminal 12-2 (FIG. 3) of the charging means 12, and is outputthrough the output terminal 12-1 when the switching element, which isthe charging means 12, is turned on by a control voltage Vg applied tothe on/off control terminal Cont. Therefore, all the capacitorsconnected to the output terminal 12-1 of the charging means 12 arecharged with the pre-charging voltage Vpre.

Therefore, when the charging means 12 is turned off by dropping thecontrol voltage Vg of the charging means 12 from a high level to a lowlevel after the point P of FIG. 4 is charged, the point P, which is thetouch detecting unit, becomes Hi-Z, such that electric charges at thepoint P are isolated in the touch capacitor, the equivalent capacitorCeq between lines, and the parasitic capacitor Cp. An example, when analternating voltage is applied to the equivalent capacitor Ceq betweenlines, a magnitude of the voltage detected at the point P is inproportion to a magnitude of the alternating voltage applied to theequivalent capacitor Ceq between lines, and has a correlation withcapacitances connected to the point P.

FIG. 5 is a view illustrating an example in which a touch sensoraccording to an exemplary embodiment of the present invention applies analternating voltage to an equivalent capacitor Ceq between lines inorder to detect a touch signal.

Referring to FIG. 5, the touch capacitance Ct formed between the touchsensor 10 and the conductor such as the finger 25, Ceq, Cvcom, and Cpare connected to the output terminal 12-1 of the charging means 12.Therefore, when the pre-charging signal Vpre is applied to the inputterminal 12-2 of the charging means 12 in a state in which the chargingmeans 12 is turned on, Ceq, Ct, and Cp are charged with a pre-charginglevel Vpre, such that a potential of an input terminal of the touchdetecting unit 14 becomes the pre-charging level Vpre. Then, when thecharging means 12 is turned off, signals charged in the three capacitorsare maintained in the pre-charging signal level Vpre unless they areseparately discharged.

In order to stably isolate the charged signals, the output terminal 12-1of the charging means 12 and the input terminal of the touch detectingunit 14 are in a Hi-z state.

The touch detecting unit 14 detects a voltage of the sensing pad 10 a(or a voltage of the point P). The touch detecting unit 14 detects avoltage of the point P when the touch is not generated (that is, when Ctis not formed), and detect a voltage of the point P when the touch isgenerated (that is, when Ct is formed), and obtains the touch signalusing a magnitude difference between the detected two voltages. Althougha sensing signal line resistor Rt is present between the sensing pad 10a and the input terminal of the touch detecting unit, which is the pointP, in an example of FIG. 5, since magnitudes of the signal across Rt arethe same as each other after a predetermined time point, an influence ofRt is ignored. Therefore, in the present disclosure, the voltagedetected in the sensing pad 10 a and the voltage detected at the point Phave the same meaning.

In an exemplary embodiment of the present invention, when the point P ofFIG. 5 is charged with the charging voltage Vpre, a predeterminedvoltage Vl and Vh is connected to one side of the non-sensing pad signalline 22 b connected to the non-sensing pad 10 b. Vl is a low voltage ofan alternating voltage according to an exemplary embodiment of thepresent invention, Vh is a high voltage of the alternating voltageaccording to an exemplary embodiment of the present invention, and Vhand Vl are swung in the alternating voltage. Vh and Vl serve as Vlbldescribed above, that is, serve to form an equivalent capacitor Ceqbetween lines.

The alternating voltage is applied to the non-sensing pad signal line 22b in order to detect a touch signal when a predetermined time elapsesafter the charging voltage Vpre is applied. An absolute magnitude of thealternating voltage is Vh-Vl, and a potential may be changed from a highvoltage Vh to a low voltage Vl or from the low voltage Vl to the highvoltage Vh. The alternating voltage has various shapes such as a squarewave shape, a triangular wave shape, a sine wave shape, a sawtooth waveshape, or the like, and the TDI according to an exemplary embodiment ofthe present invention may vary a magnitude or a frequency of thealternating voltage.

The touch detecting unit 14 detects the voltage in synchronization witha rising edge or a rising time in which the alternating voltage risesfrom the low voltage Vl to the high voltage Vh or a falling edge or afalling time in which the alternating voltage falls from the highvoltage Vh to the low voltage Vl. It is preferable that the TDI detectthe voltage after a predetermined time is delayed from the rising orfalling edge when detecting the voltage in synchronization with therising or the falling edge. The reason is that some time (for example,several tens of nano seconds or several tens of micro seconds) isrequired until the detected voltage is stabilized by a resistancecomponent Rt of the sensing pad signal line 22 a and a resistancecomponent Rnt of the non-sensing pad.

In addition, since an electromagnetic wave generated in the rising edgeor the falling edge of the alternating voltage may have an influence onan apparatus coupled to a capacitive touch detecting means according toan exemplary embodiment of the present invention, the TDI according toan exemplary embodiment of the present invention may further include ameans adjusting a gradient of the alternating voltage in the rising edgeor the falling edge. A register may be used as an example of the meansadjusting the gradient in the TDI. A time in the rising edge or thefalling edge is mapped to a plurality of registers, and when one of theplurality of registers is selected, an alternating voltage generatingunit 42 of FIG. 9 adjusts the gradient of the alternating voltage in therising edge or the falling edge.

When the point P of FIG. 5 is charged with the charging voltage Vpre, ifit is assumed that a voltage applied to the no-sensing pad signal line22 b is Vh or Vi, the equivalent capacitor Ceq between lines is chargedwith a voltage corresponding to a difference between Vpre and Vh or adifference between Vpre and Vl. For example, when Ceq is charged withVpre, if an initial voltage connected to the non-sensing pad signal line22 b is the high voltage Vh, the alternating voltage is swung from thehigh voltage Vh to the low voltage Vl, and a polarity of the alternatingvoltage is negative (−). In addition, when Ceq is charged with Vpre, ifan initial voltage connected to the non-sensing pad signal line 22 b isthe low voltage Vl, the alternating voltage is swung from the lowvoltage Vl to the high voltage Vh, and a polarity of the alternatingvoltage is positive (+).

In the following Equation 1 and Equation 2, a capacitance, which is amagnitude of Ct, is changed depending on whether or not the touch isgenerated or depending on an overlap distance or an overlap area betweenthe touch means and the touch sensing pad 10 a, and a value of Ct in thefollowing Equation 1 and Equation 2 when the touch is not detected isnot present. In an exemplary embodiment of the present invention, adifference between the detected voltage when the touch is not generated,that is, when Ct is not generated, and a voltage value when the touch isgenerated, that is, CT is generated, is detected to detect whether ornot the touch is generated or a touch area. Therefore, it is preferableto store a voltage value in a non-touch state, which is a fixed value,in a storage device (a memory 28 of FIG. 9).

When a voltage detected by the touch detecting unit 14 when all thetouch sensors 10 are not touched is stored in the memory and adifference between this voltage and a voltage detected by the touchdetecting unit when the corresponding touch sensor is operated as thesensing pad is detected, it is possible to easily detect whether or notthe touch is generated and the touch area.

Meanwhile, Vh and Vl are generated in a power supply unit 47 of FIG. 9in the TDI, and alternatings of Vh and Vl is generated in thealternating voltage generating unit 42 of FIG. 9 in the TDI.

Signal detected when Ceq is not used and alternating voltage is appliedto G/L

$\begin{matrix}{{D\text{/}B} = {{Vpre} \pm {{Vdrv}\frac{{Cdrv} + {Cgl}}{{Cdrv} + {Cgl} + {Cp} + {Ct}}}}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

Signal detected when Ceq is used and alternating voltage is applied toG/L

$\begin{matrix}{{D\text{/}B} = {{Vpre} \pm {{Vdrv}\frac{{Ceq} + {Cgl}}{{Ceq} + {Cgl} + {Cp} + {Ct}}}}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

Sensed voltage detected in synchronization with AC input power

$\begin{matrix}{{D\text{/}B} = {{Vpre} \pm {{Vc}\; 2\frac{Ct}{{Cgs} + {Cp} + {Ct}}}}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

Ct of Equation 1 or Equation 2 may be obtained from the followingEquation 4.

$\begin{matrix}{{Ct} = {{\varepsilon 2}\frac{S\; 2}{D\; 2}}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$

In Equation 4, ε₂ may be obtained from a medium between the touch sensor10 and the finger 25, and may be calculated by a complex permittivity ofa plurality of media when the plurality of media are used. S₂corresponds to an overlap area between the sensing pad 10 a and thefinger 25. When the finger 25 covers the entirety of any sensing pad 10a, S₂ corresponds to an area of the touch sensor 10. When the finger 25covers a portion of the touch sensor 10, S₂ will correspond to an areareduced from an area of the sensing pad 10 a by an area that does notoverlap with the finger 25. In addition, D₂ is a distance between thesensing pad 10 a and the finger 25, and will thus correspond to athickness of the protection layer 24 put on an upper surface of a touchscreen panel 50.

In addition, since the touch sensors 10 and the sensor signal lines 22according to an exemplary embodiment of the present invention aredisposed in a display device, a detailed study on a structure of thedisplay device is required. Although the display device will bedescribed on the basis of an LCD in the present disclosure, a thin filmtransistor (TFT) substrate of an AMOLED is similar to that of the LCD,and thus, the spirit of the present invention described in the presentdisclosure is similarly applied to the AMOLED. In addition, since signallines and pixels are included in all display devices such as a PMOLED, aPDP, or the like, and the present disclosure is a concept of disposingan embedded touch screen based on the signal lines and the pixels, thespirit of the present invention is applied to all the display devices.

FIG. 6 is a view illustrating a structure of an LCD. Referring to FIG.6, the LCD is formed by attaching a color filter substrate 100 and a TFTsubstrate 200 to each other by a sealant (not illustrated). In the TFTsubstrate, three sub-pixels of red/green/blue form one pixel, which actsas a basic pixel unit and is also called a dot. In each of thesub-pixels, a pixel electrode, which is a transparent electrode formedof indium tin oxide (ITO), or the like, is connected to a drain of a TFT220, and a source line 250 formed of a source metal is connected to asource of the TFT. In addition, a gate line 240 formed of a gate metalis connected to a gate of the TFT.

Color filters 110 such as red color filters R, green color filters G,and blue color filters B are formed on the same lines as those of thesub-pixels of the TFT substrate 210, and a black matrix (BM) 130 forshielding the gate lines 240 or the source lines 250 of the TFT isformed among the R/G/B.

FIG. 7 is a view illustrating a detailed structure of a thin filmtransistor (TFT) of FIG. 6. Referring to FIGS. 6 and 7, a gate metallayer formed of a metal component such as copper, aluminum, molybdenum,chromium, or the like, forms the gate line 240 on an upper surface ofthe TFT substrate 210 formed of glass, plastic, or the like. A sourceelectrode 270 and a drain electrode 260 of the TFT are formed by asource metal layer formed of a metal component such as copper, aluminum,molybdenum, chromium, or the like, above the gate line. In addition, thesource line 250 is formed on the same layer by the same source metallayer in the source electrode 270 of the TFT, and transfers an imagesignal to a pixel electrode 230.

The drain of the TFT 220 is connected to the pixel electrode to form Clcand Cst, and a liquid crystal (not illustrated) reacts by a potentialdifference between the pixel electrode 230 and a common electrode 120 toform image quality. Since an operation principle and a detailedstructure of the TFT 220 are obvious to those skilled in the art,contents unrelated to the present invention are not described, buttechnical contents obvious to those skilled in the art are reflected inall technical contents of the present disclosure.

Although an example in which the TFT 220 has a TN structure isdescribed, in the case of an LCD using a transversal electric field modesuch as an in-plane switching (IPS) mode, a fringe field switching (FFS)mode, or the like, the operation principle of the LCD described abovemay be similarly applied except that the common electrode 120 of FIG. 1is positioned on the same layer as that of the TFT substrate 210.

The touch screen of the display device having the embedded touch screenaccording to an exemplary embodiment of the present invention does notbasically interwork with an operation of the display device. That is,the touch screen is operated asynchronously with a driving mechanism ofthe LCD. In the case in which signals of the touch screen and thedisplay device according to an exemplary embodiment of the presentinvention have a correlation therebetween, a driving frequency of thedisplay device is about 60 Hz, such that it is not easy to synchronizean operation frequency of a touch generally requiring a drivingcondition of 100 Hz or more. In addition, in the case of using a methodof sensing a touch plural times and removing noise using various filterswhen static electricity, noise, or the like, is introduced into thetouch sensor, when the touch screen is synchronized with the LCD, thetouch screen is subordinated to a frequency of the LCD, such that a casein which it is impossible to detect the touch plural times in a limitedtime may occur.

In order to solve the problem described above, the touch screenaccording to an exemplary embodiment of the present invention isembedded in the display device, but is operated separately from adriving mechanism of the display device. In some cases, it may beadvantage to synchronize the touch screen with a driving signalmechanism of the display device to detect a touch signal. This case is,for example, a case of improving touch detection sensitivity bysynchronizing a ground or changing a specific signal of the LCD.Therefore, the touch screen according to an exemplary embodiment of thepresent invention supports both of a mode in which it is synchronizedwith a signal (for example, data enable (DE), Hsync, or Vsync) of thedisplay device and a mode in which it is not synchronized with thesignal.

FIG. 8 illustrates a first exemplary embodiment about embedding of thetouch screen in the display device having an embedded touch screen, andin the display device according to an exemplary embodiment of thepresent invention in which a first substrate 100 on which the colorfilters 110 and the common electrodes 120 are formed and a secondsubstrate 200 in which the pixel electrodes 230 and the driving signallines are formed are disposed to overlap with each other, a sensor layerincluding the touch sensors 10 sensing touch signals and sensor signallines 22 is formed below the driving signal lines.

That is, in this case, the sensor layer is installed between the gateline 240 and the source line 250 constituting the TFT substrate 210 andthe TFT 220, and a sensor layer first deposited is formed of aconductive material, and is formed of a metal component such aschromium, copper, aluminum, molybdenum, or the like, or a transparentconductive material such as ITO, CNT, a metal mesh, or the like.

In addition, the touch sensors 10 are patterned and disposed on thesensor layer in a structure in which a plurality of isolated areas areregularly arranged in longitudinal and transversal directions asillustrated in FIG. 9, and the sensor signal lines 22 connecting thetouch sensors 10 and a TDI 30 to each other are also disposed on thesensor layer.

In addition, the touch sensors 10 according to an exemplary embodimentof the present invention are disposed at a width wider than those of thegate lines 240 and the source lines 250, may be patterned in a matrixstructure in which the plurality of isolated areas are regularlyarranged in the longitudinal and transversal directions as illustratedin FIG. 9, and the sensor signal lines 22 connecting the touch sensors10 and the TDI 30 to each other are also disposed.

Although the touch sensors 10 are installed in five columns in thelongitudinal direction and in six rows in the transversal direction inan exemplary embodiment of the present invention, this is only anexample, and several tens to several hundreds of touch sensors 10 may beinstalled in the longitudinal and transversal directions at the time ofactually using the display device.

In addition, it is preferable that insulators are deposited andinstalled on upper surfaces of the touch sensors 10.

The touch sensors 10 according to an exemplary embodiment of the presentinvention described above are positioned only below the gate lines 240and the source lines 250, which are signal lines of the LCD, and aredisposed at positions that do not overlap with the pixel electrodes 230in the vertical direction.

This is to prevent deterioration of image quality caused by distortiongenerated in a voltage applied to the liquid crystal by a capacitor dueto coupling between the pixel electrodes 230 and the touch sensors 10when a rising or falling voltage is applied in order to detect a touchof the touch sensors 10.

However, this structure is appropriate for using an AMOLED or a PMOLEDthat does not use the liquid crystal.

In a first exemplary embodiment of the present invention, the touchsensors 10 are positioned between the TFT substrate 210 and the gate andsource lines 240 and 250. In this case, it is preferable that a width ofthe touch sensor 10 is wider than those of the gate line 240 and thesource line 250. Further, it is preferable that a width of the touchsensor 10 is as wide as possible in a range in which the touch sensor 10does not have an influence on the liquid crystal. The reason is thattouch sensitive may be improved by widely forming a sensing area of thetouch sensor 10.

In addition, the touch sensors 10 may also be disposed at edges of thepixel electrodes 230 in a range in which they do not intersect with thepixel electrodes 230 in the vertical direction. In addition, the touchsensors 10 may also be disposed below metals forming storage capacitorsCst. The metals forming the storage capacitors Cst are generally formedof the gate lines 240, and since DC is always applied to the gate lines240, the gate lines 240 are not affected by driving signals of thesensor signal lines 22 positioned under the gate lines 240.

In addition, in a first exemplary embodiment of the present invention,the touch sensors 10 are disposed in a sub-pixel unit. That is, thetouch sensors 10 may be positioned somewhere below the gate lines 240and the source lines 250 configuring the sub-pixels, and the touchsensors 20 or the sensor signal lines 22 are not installed below certainsub-pixels in order to partition the touch sensors 10.

The sensor signal lines 22 according to an exemplary embodiment of thepresent invention may be formed of indium tin oxide (ITO), carbon nanotube (CNT), indium zinc oxide (IZO), zinc tin oxide (ZTO), nano wire,silver nano wire, or the like, which is a transparent conductivematerial. The reason is that a flash phenomenon is generated by light oran aperture ratio of the LCD is reduced when the sensor signal lines 22are formed of an opaque metal.

According to an exemplary embodiment of the present invention, when thetouch sensors 10 are positioned below the gate lines 240 and the sourcelines 250, which are the signal lines of the LCD, the term “below” isappropriate in the case in which the TFT substrate 210 is disposed at alower position as illustrated in FIG. 3. When the TFT substrate of FIG.3 is overturned by 180 degrees, such that the TFT substrate is disposedat a higher position and the TFT 220 and the touch sensor layer arepositioned below the TFT substrate 210, the touch sensors 10 may bepositioned above the gate lines 240 and the source lines 250. In thepresent disclosure, upper and lower portions are defined on the basis ofthe case in which the TFT substrate 210 is disposed at the lowerposition. Therefore, even though the TFT substrate 210 is overturned tomove to the higher position, such that the upper and lower portions areexchanged with each other, absolute directions of the upper and lowerportions are determined on the basis of the case in which the TFTsubstrate is disposed at the lower position.

In FIG. 10 illustrating an example of a configuration of the touchsensors 10 in the display device having an embedded touch screenaccording to an exemplary embodiment of the present invention, the touchsensors 10 are divided into 34 partitions in the transversal directionand into 42 partitions in the longitudinal direction, and the numbers ofsub-pixels in the transversal direction and the longitudinal directionare 34 and 42, respectively. When it is converted into a resolution ofthe LCD, the resolution is 11 (H)×42 (V). Therefore, when taking intoconsideration that a high definition (HD) resolution is 1280 (H)×800(V), the display device having an embedded touch screen according to anexemplary embodiment of the present invention is a display device havinga significantly small size. (In an exemplary embodiment, one sub-pixelremains in an H direction). A display device of 11×42 has been setregardless of a size by way of example in the present exemplaryembodiment, and display devices having various resolutions are actuallyused.

In FIG. 10, only the gate lines 240 and the source lines 250 are shownin the display device of 11×42 and the touch sensors 10 according to thepresent invention defined in FIG. 3 are shown below the gate lines 240and the source lines 250. Thick lines indicate the touch sensors 10 andthe sensor signal lines 22, and show that the touch sensors 10 and thesensor signal lines 22 are positioned below the gate lines 240 and thesource lines 250.

In the case in which the touch sensors 10 are formed in the matrixstructure as illustrated in FIG. 9, the touch sensors 10 may also beformed in a structure without having the mesh structure, but may beformed in the mesh structure as illustrated in FIG. 10. As anotherexample, in the case in which the touch sensors 10 are formed in thematrix structure, the touch sensors 10 are may be formed in a mixturestructure of the mesh structure and a non-mesh structure. That is, someof the touch sensors 10 may not be formed in the mesh structure, and theother of the touch sensors 10 may be formed in the mesh structure.

In addition, the touch sensors 10 have areas that become small as theybecome close to the TDI, and are formed in a mesh structure, asillustrated in FIG. 10. When the touch sensors 10 are formed in the meshstructure, even though disconnection is partially generated due to aprocess defect, a probability that the touch sensors 10 will malfunctionis significantly reduced.

In an exemplary embodiment of the present invention, the number ofsensor signal lines 22 is one or plural, and referring to a touch sensor10 disposed at a left lower end and a touch sensor 10 disposed at aright upper end, the sensor signal lines 22 are formed to have twobranches in an exemplary embodiment of the present invention. The sensorsignal lines 22 having the two branches may be bonded to each other inthe active area in which the touch sensors 10 are installed or be bondedto each other in the BM area, that is, the non-active area, of the LCDin which the TDI is installed. This is used as a method of improving ayield of a product since another sensor signal line 22 may be used eventhough disconnection is generated in one sensor signal line 22. When theplurality of sensor signal lines 22 are used with respect to one touchsensor 10 as described above, a probability that a problem will occur indetecting a touch may be reduced even though disconnection due to aprocess defect is generated in the sensor signal line.

In addition, in a first exemplary embodiment of the present invention,the touch sensors 10 are applied with the alternating driving voltagegenerated from the TDI 30 or the AC alternating voltage generated fromthe PMIC, and the touch detecting unit 14 detects the touch signals insynchronization with a rising or falling edge of the AC alternatingvoltage.

Again referring to FIG. 8, an insulator is present between the sensorsignal line 22 and the gate line 240 or the source line 250, and aparasitic capacitance is formed between the sensor signal line 22 andthe driving signal lines (the gate and source lines 240 and 250) throughthe medium of the insulator (hereinafter, a parasitic capacitance formedbetween the touch sensor 10 and the gate line 240 is called Cg, aparasitic capacitance formed between the touch sensor 10 and the sourceline 250 is called Cs, and an equivalent parasitic capacitance obtainedby the sum of Cg and Cs is called Cgs). Cgs is a total parasiticcapacitance formed between one touch sensor and the gate and sourcelines 240 and 250. The insulator has several tens of angstroms (10⁻¹⁰)or several micrometers (μm), and referring to Equation of FIG. 22, aparasitic capacitor Cg, Cs, or Cgs have a value hundred times or morelarger than that of a touch capacitance Ct detected by a touch. A touchsensor connected to the other side of the parasitic capacitanceCg/Cs/Cgs is affected by a variation in an analog voltage of a signalline connected to one side of the parasitic capacitance Cg/Cs/Cgs, thatis, the source line 250 or a variation in gate-on/off voltages of thegate line 240, such that it is impossible to detect a touch signal.Therefore, a method of allowing the touch sensor 10 not to be affectedby the source line 250 or the gate line 240 is required.

FIG. 11 is a view illustrating a display device having an embedded touchscreen according to a second exemplary embodiment of the presentinvention. The display device having an embedded touch screen accordingto a second exemplary embodiment of the present invention furtherincludes a guard layer (G/L) 295 preventing interference of signalsbetween a touch screen and a signal line.

The guard layer 295 is formed between the touch sensor 10 disposed atthe lowermost side and the driving signal lines (the gate and sourcelines 240 and 250) constituting the TFT, and overlaps with the touchsensor 10 in a one-to-one scheme as illustrated in FIG. 10 (however, theguard layer 295 does not overlap with the touch sensor 10 in aone-to-one scheme in a TDI or LDI bonding part except for an A/A). Thesame voltage as a voltage applied to the sensing pad 10 a or thenon-sensing pad 10 b is applied to the guard layer 295. Alternatively,the alternating AC voltage is applied to the guard layer 295.

The G/L 295 according to an exemplary embodiment of the presentinvention described above is not installed only below the source line250 or the gate line 240, but may be installed over an entire area ofthe display device. However, in this method, the voltage applied to theG/L 295 may have an influence on a pixel area of the display device tocause deterioration of image quality.

In a second exemplary embodiment of the present invention, a firstinsulator 285 is installed on upper surfaces of the touch sensors 10.The first insulator 285 is a material electrically insulating the touchsensor 10 and the G/L 295 from each other. The first insulator 285 maybe formed only between the touch sensors 10 and the G/L 295, asillustrated in FIG. 11. However, this method is not preferable since aseparate mask is required. In addition, it is preferable that the firstinsulator 285 is applied over an entire active area of the displaydevice.

In addition, in a second exemplary embodiment of the present invention,a second insulator 286 for insulating the G/L 295 from a component ofthe display device, such as the gate line 240 of the TFT, is installedon an upper surface of the G/L 295. The second insulator 286 may also bepartially patterned as in FIG. 10, but is not preferable since itrequires a separate mask, and it is preferable that the second insulator286 is applied over an entire A/A of the display device.

In an exemplary embodiment of the present invention, it is preferablethat the first insulator 285 and the second insulator 286 are formed ofthe same material, and referring to FIG. 11, pads for applying signalsat one side of the display device are opened in the sensor signal line22 and the G/L 295, and a flexible circuit board such as a flexibleprinted circuit (FPC), a chip on flexible printed circuit (COF), or thelike, is bonded through the pads. In this case, in order to expose thepad of the sensor signal line bonding part 297 and the pad fortransferring the signal to the G/L 295, the first insulator 285 and thesecond insulator 286 are etched to open the pads. In this case,patterning may be easily performed using one mask when the firstinsulator 285 and the second insulator 286 are formed of the samematerial.

In a second exemplary embodiment of the present invention, a method forapplying the driving signal to the G/L 295 includes 1) a method forapplying a DC voltage or an alternating voltage output from a TDI, and2) a method for applying the same alternating voltage as the AC voltageapplied to the TDI from a power management IC (PMIC).

1) Method for Applying DC Voltage or Alternating Voltage Output from TDI

Referring to FIG. 11, parasitic capacitance (not shown) is formedbetween the G/L 295 and the gate line 240, and parasitic capacitance(not shown) is also formed between the source line 250 or the storageelectrode (Cst electrode) and the G/L 295. When the DC voltage(including GND) which is not varied is applied to the G/L 295, eventhough a signal variation of the gate line 240 or the source line 250and a signal transfer through Cg or Cs occurs, since the G/L 295prevents the signal variation, the touch sensor 10 is not affected bythe display driving signal line. As such, according to the presentinvention, the DC voltage is applied to the G/L 295. The applied DCvoltage is transferred through the G/L bonding part 296 of FIG. 11.

In order to improve detected sensitivity of the touch sensor, thealternating voltage may be applied to the G/L 295, where the appliedalternating voltage is Vlbl of FIG. 4.

There are a plurality of methods for applying Vlbl according to astructure of the touch sensor, and the methods are as follows.

* when Cdrv inside the TDI is used without using Ceq of FIG. 4

As in the example of FIG. 4, when Vlbl is not applied to the non-sensingpad 10 b, the alternating voltage is applied to Cdrv (not shown) (whichexists inside the TDI, and has one side connected to the P point of FIG.4 and the other side applied with the alternating driving voltage), andthe touch signal is detected in synchronization with the rising orfalling edge of the alternating voltage, the precharge voltage and thealternating voltage are applied to the G/L 295. As described below,since the precharge voltage is applied earlier than the alternatingdriving voltage, when the same voltage as the precharge voltage isapplied to the G/L 295 of FIG. 11 when the precharge voltage is appliedto the P point of FIG. 4, the parasitic capacitance generated betweenthe G/L 295 and the sensing pad is removed because there is no potentialdifference between the G/L 295 and the sensing pad. Thereby, theprecharge may be faster performed.

After the precharge, the alternating driving voltage (as an example,Vlbl) is applied to one side of Cdrv, and the touch signal is detectedin synchronization with the rising or falling edge of the alternatingvoltage, where the same alternating voltage as the voltage applied toCdrv is also applied to the G/L.

Referring to FIG. 11, parasitic capacitance (not shown) is generatedbetween the G/L 295 and the touch sensor, which is defined as Cgl. Whenthe same alternating voltage as the voltage applied to Cdrv is appliedto the g/L 295, Cgl is included in a numerator of Equation of detectingthe touch signal, which is advantageous to improve the touchsensitivity, as in the following Equation.

Signal detected when Ceq is not used and alternating voltage is appliedto G/L

$\begin{matrix}{{D\text{/}B} = {{Vpre} \pm {{Vdrv}\frac{{Ceq} + {Cgl}}{{Ceq} + {Cgl} + {Cp} + {Ct}}}}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

Here, Vpre is a precharge voltage applied to the touch sensor asdescribed in the example of FIG. 4, Cdrv, which is a capacitor insidethe TDI, is a capacitor of which one side is connected to the P point ofFIG. 4 and the other side is applied with the alternating drivingvoltage, Cgl is parasitic capacitance formed between the G/L and thetouch sensor, and Cp is several parasitic capacitances connected to theP point, where parasitic capacitance formed between the sensing pad andnon-sensing pad is one among several parasitic capacitances. Vdrv, whichis the alternating driving voltage, may be the same voltage as Vlbl ofFIG. 4. A touch drive IC (TDI) detects a magnitude difference of a valuewhen Ct does not exist in Equation 2 and D/B when the touch occurs andCt occurs, and determines whether or not the touch is performed.

* when Ceq of FIG. 4 is used

As illustrated in FIG. 4, when the alternating driving voltage Vlbl isapplied to the Ceq and the non-sensing pad 10 b and the same alternatingvoltage is applied to the G/L 295, since the same Vlbl is applied acrossthe parasitic capacitance (not shown) generated between the non-sensingpad 10 b and the G/L 295, the parasitic capacitance between thenon-sensing pad 10 b and the G/L 295 does not affect the touchdetection, thereby improving sensitivity of the touch detection.Therefore, according to the present invention, the same alternatingvoltage as the voltage applied to Ceq is applied to the non-sensing pad10 b.

Thereby, the touch signal detected at the P point is as in the followingEquation.

Signal detected when Ceq is not used and alternating voltage is appliedto G/L

$\begin{matrix}{{D\text{/}B} = {{Vpre} \pm {{Vc}\; 2\frac{Ct}{{Cgs} + {Cp} + {Ct}}}}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

Here, Vpre is a precharge voltage applied to the touch sensor asdescribed in the example of FIG. 4, Ceq, which is equivalent parasiticcapacitance formed between the sensing pad and the non-sensing pad, is acapacitor of which one side is connected to the P point of FIG. 4 andthe other side is applied with Vlbl, which is the alternating drivingvoltage, Cgl is parasitic capacitance generated between the G/L and thetouch sensor, and Cp is several parasitic capacitances connected to theP point, where parasitic capacitance formed between the gate and thedrain of the switching element of FIG. 4 is one among several parasiticcapacitances. A touch drive IC (TDI) detects a magnitude difference of avalue when Ct does not exist in Equation 3 and D/B when Ct occurs due tothe touch, and determines whether or not the touch is performed.

In order to apply the alternating driving voltage such as Vlbl or Vdrvin the TDI to the G/L 295, a dedicated output pin outputting thealternating driving voltage to the TDI is required.

As such, according to the present invention, when the G/L 295 isinstalled and the DC voltage or the alternating driving voltage isapplied, it is possible to detect the touch signal with a predictableEquation independently of the driving signal of the display device.

In the present invention, since a parasitic capacitance formed betweenthe G/L 295 and the gate line 240 or the source line 250 issignificantly large, driving capability of a capacitor, which is adriving element, should be significantly large in order to drive the G/Lby an alternating voltage. In order for the TDI 30 to drive the G/L 295,a dedicated output terminal embedded in the TDI 30 should havesignificantly capacitor driving capability, which leads to an increasein a size of the TDI 30 to cause an increase in cost.

In order to solve this problem, the G/L 295 is driven using a dedicatedbuffer or operation amplifier (OPAMP) rather the TDI 30 in a secondexemplary embodiment of the present invention. Referring to FIG. 12, analternating voltage generated in a dedicated pin of the TDI is appliedto the G/L 295 through the buffer or the OPAMP. The application of theAC voltage to the G/L 295 is performed through a G/L bonding part 296 ofFIG. 11. The buffer or the OPAMP is positioned outside the TDI 30, andhas driving capability for driving a capacitor having a largecapacitance.

The buffer or the operation amplifier according to an exemplaryembodiment of the present invention, which is an electrical elementoutputting the alternating voltage received from the TDI 30 as it is,has an advantage such as large driving capability. Since the G/L 295 hasa wide area and a large resistance, when one buffer or OPAPM is used,driving capability may be insufficient. Therefore, a plurality ofbuffers or OPAMPs may be used. It is preferable that the plurality ofbuffers or OPAMPs are appropriately disposed at a corner portion, acentral portion, a left portion, or a right portion of the G/L 295 toallow magnitudes of the alternating voltage not to be different fromeach other at each position of the G/L 295.

2) Method for Applying Same Alternating Voltage as AC Voltage Applied toTDI from Power Management IC (PMIC)

TCON or LDI or TDI used in the present invention requires input powerfor an IC operation. The input power is typically 3V or 3.3V, which isdefined as Vc, and magnitude thereof is limited to 3V as an example.

In the present invention, the AC input power has a potential differenceof 3V, and is defined as power which is swung from a high to a low orfrom a low to a high on the basis of an earth ground. FIG. 13 is a viewfor defining the AC power used in the present invention. Referring toFIG. 13, the PMIC is applied with Vc1 of 3V, and Vc1 is a voltage of 3Von the basis of the earth ground, that an absolute ground. The PMIC,which is an IC forming Vc2, where Vc21, which is one side of the PMIC isgreater than Vc22, and a potential difference between Vc21 and Vc22 is3V as an example. For example, if Vc21 is 10V, Vc22 is 7V.

This relationship is illustrated in a waveform of FIG. 14. Vc21 and Vc22are swung from a high to a low or a low to a high while maintaining aconstant magnitude, which is in-phase. In the present invention, thisvoltage is defined as the AC input voltage.

Vc22 of FIG. 14 is an alternating voltage, but acts as a ground, whichis called a dynamic ground. The dynamic ground has magnitude which ischanged, and the potential difference of the AC input voltage based onthe dynamic ground is always maintained to be constant.

An output voltage of the PMIC of FIG. 13 is variously output. Any outputvoltage is possible as long as Vc21 and Vc22 are any value (here, 3V),which is Vc2. For example, if Vc21 is 20V, Vc22 is 17V. In addition, ifVc21 is 8V, Vc22 is 5V.

The AC input voltage typically alternates two states. Here, a smallvoltage is referred to as a low voltage, and a large voltage is referredto as a high voltage (Hi voltage). The AC input voltage alternates fromthe low voltage to the high voltage or from the high voltage to the lowvoltage. There are three or more alternating states. The PMIC may beswung while changing voltages of the plurality of states insynchronization with a control signal (not shown) output from the TDI orTCON. As described below, the TDI detects the touch based on thealternating of the AC input voltage applied to the TDI.

FIG. 13 illustrates an example of a circuit in which the AC inputvoltage is applied to the TCON and the LCD drive IC (LDI) and the TDIused in the display device having an embedded touch screen according toan embodiment of the present invention. Referring to FIG. 13, Vc2 formedin the PMIC is applied to the TCON and the LDI and the TDI, andmagnitude thereof is 3V as an example. Vc22 is the dynamic groundserving as a ground. As an example, the AC input voltage alternates twostates in which Vc21 is 10V and Vc22 is 7V, from a high to a low or froma low to a high.

In FIG. 13, an L/S, which is a level shifter, is a circuit elementtransferring a video signal of a graphic card or a CPU in a system (notshown) to the TCON or the LDI. In order to use the level shifter totransfer the signal of the case in which there are two grounds, the twogrounds are required in view of those skilled in the art, and in thepresent exemplary embodiment, an absolute ground and Vc22 are used.Since there is also a case in which the ICON provides the video signalto the LDI in any exemplary embodiment, in this case, the L/S existsbetween the ICON and the LDI, and Vc1 is applied to the ICON as in theabsolute ground.

Again referring to FIG. 13, many voltages, which is reasonable for thoseskilled in the art, such as a voltage of about −20V, which is a gate offvoltage, a voltage of 12V, which is a gate on voltage, and 5V, which isa common voltage, are generated from a power terminal in the LDI of FIG.13. Since the ground of the LDI is the dynamic ground (Vc22), manyvoltages generated in the LDI will form a potential on the basis of thedynamic ground. For example, the meaning that the common voltage is 5Vmeans that the common voltage is 12V when magnitude of Vc22, which isthe dynamic ground, is 7V, and the common voltage is 8V when Vc22 is 3V.

This aspect is also applied to the TDI and the G/L according to thepresent invention. The TDI generates Vlbl, or Vpre, or various referencevoltages defining the ADC or the DAC, where since the ground of the TDIis also applied with Vc22, which is the dynamic ground, in the case inwhich absolute magnitude of Vlbl on the basis of the earth ground is 8V,if Vc22 is 7V, relative magnitude of Vlbl to Vc22 is 15V. In addition,when Vc22 is swung from 7V to 3V, Vlbl is also swung from 16V to 11V.

When the AC input voltage is applied to the LDI, the TDI, the ICON, andthe G/L as illustrated in FIG. 15, since the Vc22, which is the dynamicground, applied to the LDI, the TDI, the ICON, and the G/L is swung withreference to FIG. 8, it may be appreciated that the source line or thegate line is also swung in synchronization with Vc22, but magnitude ofthe signal is maintained to be constant as in the waveform of FIG. 14.In addition, the touch sensor is also swung in synchronization withVc22.

After Vpre is applied to the touch sensor and Vc2 is swung from the lowto the high or from the high to the low while maintaining the constantvoltage, the parasitic capacitance generated between the driving signalline and the touch sensor of FIG. 8 does not affect the touch detection.

When it is assumed that the magnitude of the voltage at which the ACinput power is swung is Vc2 when Vlbl of FIG. 4 is not operated, thetouch signal is detected from the touch pad in synchronization with thealternating of the AC input voltage, which is indicated by Equation 4.

Sensed voltage detected in synchronization with AC input power

$\begin{matrix}{{Ct} = {{\varepsilon 2}\frac{S\; 2}{D\; 2}}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$

Here, Vc2 is magnitude of the voltage at which the LDI and the TDI areswung on the basis of Vc22, which is the dynamic ground which issimultaneously applied to the LDI and TDI, Cgs is equivalent parasiticcapacitance of the parasitic capacitance formed between the touch sensorand the signal line, Ct is touch capacitance detected from the touchsensor 10 by an object such as a finger, and Cp is parasitic capacitanceadded to the sensing pad 10 a.

Since there is no Cgs in Equation 4, it may be appreciated thatsignificantly large touch sensitivity may be obtained for Cp having arelatively small value. However, a touch detection method insynchronization with the AC input power has a disadvantage that itrequires the PMIC or the level shifter.

If the touch signal is detected in synchronization with the AC inputvoltage, it is preferable that an edge signal of Vlbl is first drivenand the AC power is then swung when the touch is detected by interveninga rising edge or a falling edge of Vlbl of FIG. 4. A time difference atthis time is within about 0.1 μs to 30 μs.

In a second exemplary embodiment of the present invention, the touchsensors 10 are applied with the alternating driving voltage generatedfrom the TDI 30 or the AC alternating voltage generated from the PMIC,and the touch detecting unit 14 detects the touch signals insynchronization with a rising or falling edge of the AC alternatingvoltage.

In addition, the same voltage as the AC alternating voltage synchronizedat the time of detecting the touch signal by the touch detecting unit 14is applied to the G/L.

Referring to FIG. 9, FIG. 9 is an example of the touch screen panelaccording to an exemplary embodiment, and at a lower end of FIG. 9, aconfiguration of the touch drive IC (TDI) 30 is illustrated. The TDI 30may include a driving unit 31, the touch detecting unit 14, a timingcontrolling unit 33, a signal processing unit 35, a memory unit 28, analternating voltage generating unit 42, a power supply unit 47, and acommunicating unit 46, and may further include a CPU 40. The CPU 40 is amicroprocessor having a calculation function, and may also be positionedoutside the TDI 30.

The driving unit 31 includes the charging means 12, and includes afunction of selecting the sensing pad and the non-sensing pads among aplurality of touch sensors 10 and connecting the selected sensing padand non-sensing pads to the touch detecting unit 14. In addition, thedriving unit 31 includes a function of one side of the non-sensing padsignal line to Vh or V1 during a charging operation using the chargingmeans 12.

The timing controlling unit 33 serves to generate a plurality ofdifferent clocks required in the TDI 30. For example, clocks arerequired in order to operate the CPU 40, and are also required in orderto operate the ADC or sequentially operate multiplexers of the drivingunit 31. Several kinds of clocks are required for each function asdescribed above, and the timing controlling unit 33 may generate andsupply the plurality of various clocks as described above.

The signal processing unit 35 transfers an ADC value generated in thetouch detecting unit 14 to the CPU 40, controls the communicating unit46 to transmit the ADC value to the outside of the TDI 30 throughinter-integrated circuit (I2C) or serial peripheral interface bus (SPI)signal lines, or generates and supplies signals required in allfunctional elements in the TDI 30, such as the touch detecting unit 14,the driving unit, or the like. Functional elements or functional blocksindicate components performing the respective functions illustrated inFIG. 9. For example, currently, nine functional blocks are included inthe TDI, and the CPU 40 is one of the nine functional blocks. The signalprocessing unit 35 stores the ADC value generated in the touch detectingunit 14 in the memory unit 28, and/or performs a required calculation.For example, the signal processing unit 35 may calculate a touch areadue to the touch between the touch sensor 10 and the touch means withreference to the ADC value generated in the touch detecting unit 14, andmay also calculate a touch coordinate using the ADC value or thecalculated touch area value.

The memory unit 28 may be formed of a flash memory, an electricallyerasable programmable read only memory (EEPROM), a static random accessmemory (SRAM), or a dynamic RAM (DRAM). Several register values requiredfor driving the TDI 30 or programs required for operating the CPU 40 arestored in the flash memory or the EEPROM.

Many functions of The CPU 40 may overlap with functions performed by thesignal processing unit 35. Therefore, the CPU 40 may not be included inthe TDI 30 or may be positioned outside the TDI 30. Any one of the CPU40 and the signal processing unit 36 may not be temporarily used in asection in which it is expected that the CPU 40 and the signalprocessing unit 36 will redundantly perform their functions.

The CPU 40 may perform most of the functions performed by the signalprocessing unit 35, and extract a touch coordinate, performs a gesturesuch as zoom, rotation, movement, or the like, or performs severalfunctions. In addition, the CPU 40 may calculate an area of a touchinput to generate a zooming signal, calculate strength of the touchinput, and process data in various forms in which only a graphic userinterface (GUI) object desired by a user (for example, a GUI object ofwhich a large area is detected) in the case in which GUI objects such asa keypad are simultaneously touched is recognized as an effective inputand use the processed data in the TDI 30 or transmit the processed datato the outside through communication lines.

A program for controlling the CPU 40 may be installed in the memory unit28 and be replaced by a new program when corrections are generated. Thenew program may be executed using communication bus included in thecommunicating unit 46, for example, serial communication such as an I2C,an SPI, a universal serial bus (USB), or the like, or parallelcommunication such as a CPU interface (hereinafter, referred to as I/F),or the like.

The communicating unit 46 performs a function of outputting requiredinformation to the outside of the TDI 30 or inputting informationprovided from the outside of the TDI 30 to the inside of the TDI. In thecommunicating unit, the serial communication such as the I2C, the SPI,or the like, or the parallel I/F such as the CPU I/F, or the like, isused.

The alternating voltage generating unit 42 generates the alternatingvoltage applied to the equivalent capacitor Ceq between lines. The highvoltage Vh and the low voltage Vl of the alternating voltage aregenerated by the power supply unit 47, and the alternating voltagegenerating unit 42 combines the high voltage Vh and the low voltage Vlwith each other to generate the alternating voltage, thereby allowingthe driving unit 31 to use the alternating voltage. In addition, thealternating voltage generating unit 42 has a means adjusting thegradient of the alternating voltage in the rising edge or the fallingedge.

In an example as illustrated in FIG. 9, the number of sensing padsdetecting the touch signal is one or plural, and it is preferable thatthe number of sensing pads is plural in terms of reducing a sensingtime. The sensing pads may be randomly selected among thirty touchsensors 30 disposed in six rows Row1 to Row6 and five columns Col1 toCol5, and may be selected column-by-column or be selected row-by-row. Inan exemplary embodiment of the present invention, coordinates of rowsand columns are set on the basis of a position of the TDI. Therefore,the coordinates of the rows and the columns of the touch detectingsensors are not fixed, but may be relatively changed depending on asetting position of the TDI.

In an example in which the sensing pads are selected column-by-column,when six touch sensors 10 included in Col1 are determined to besimultaneously initial sensing pads, all of the six touch sensors 10included in Col1 are operated as the sensing pads. (In this case, touchsensors included in Col2 to Col6) are operated as the non-sensing pads.)However, in this case, the equivalent capacitor Ceq between linesdescribed above is not formed or has a small capacitance even though itis formed, such that touch detection sensitivity becomes small.Therefore, it is preferable that the touch is sensed row-by-row ascompared with column-by-column. The reason is that when the touch issensed row-by-row, adjacent sensing pad signal lines 22 are not present,such that a malfunction due to interference of signals is not generated.

All of the touch sensors 10 included in Row2 to Row6 are operated as thenon-sensing pads during a period in which five touch sensors 50 includedin Row1 are selected and operated as the sensing pads. When the fivetouch sensors 50 included in Row1 completes functions of the sensingpads, a process in which five touch sensors 50 included in Row2 becomethe sensing pads and touch sensors 50 included in Row1 and Row3 to Row6are operated as the non-sensing pads is sequentially repeated. Since thefive touch sensors 10 included in Row1 are operated as the sensing pads,it is preferable that five driving units 31 are present in the TDI.Therefore, the five sensing pads are simultaneously driven, therebymaking it possible to reduce a touch detection time.

Meanwhile, referring to the first feature of two features of the sensingequivalent capacitor Ceq between lines described above, a sensingequivalent capacitance Ceq when the five touch sensors 50 included inRow1 are operated as the sensing pads is larger than a sensingequivalent capacitance Ceq when the five touch sensors 50 included inRow6 are operated as the sensing pads. The reason is that a length ofthe sensor signal lines 22 connected to the touch sensors 10 positionedin Row1 is longer than that of the sensor signal lines 22 connected tothe touch sensors 10 positioned in Row6. Since magnitudes of the sensingequivalent capacitances Ceq formed in the sensing pads becomes large asthe sensing pads become distant from the TDI, it is preferable tocompensate for different magnitudes of the sensing equivalentcapacitances Ceq in order to detect a uniform touch signal. The meaningof the compensation for the magnitudes of the sensing equivalentcapacitances Ceq is to allow the same voltage to be detected even thoughpositions of the sensing pads are different from each other with respectto the same touch capacitance Ct by adding a compensation capacitor tothe sensing equivalent capacitance Ceq of Equation 1 or Equation 2.

The display device having an embedded touch screen according to anexemplary embodiment of the present invention has a means compensatingfor the different magnitudes of the sensing equivalent capacitances Ceqso that the same touch sensitivity is maintained in each position on thebasis of the magnitudes of the sensing equivalent capacitances Ceqdifferent from each other in each position.

FIG. 16 is a view for describing a method of applying required signalsto a display device, a touch sensor 10, and the G/L 295 in the displaydevice having an embedded touch screen according to an exemplaryembodiment of the present invention. In FIG. 16, part X is an area inwhich an image is displayed or the touch sensors 10 according to areinstalled, and will be called an active area or an A/A in the presentdisclosure. The first pads 310 of FIG. 16 are pads to which signals forthe display device are applied, and signals transferred from the LDI areapplied to the first pads 310. In addition, the second pads 320 receivesignals transferred from the TDI, the buffer, or the like, and areconnected to the G/L 295. In addition, the third pads 330 are padsconnected to the touch sensors 10.

In FIG. 16 illustrating an example about connection of signal lines,signal lines of the display device transferred from the LDI are denotedby solid lines, signals transferred to the touch sensors are denoted bydotted lines, and signals transferred to the G/L are denoted by doublesolid lines. Since the respective signal lines are positioned ondifferent layers, a short-circuit is not generated.

In addition, in the display device having an embedded touch screenaccording to an exemplary embodiment of the present invention, differentsubstrates, for example, flexible circuit boards such as FPC or COF maybe attached onto pads for transferring the signals to the LDI, the TDI30, and the G/L 295, respectively. Alternatively, one flexible circuitboard may be attached onto the pads in order to reduce costs.

Further, although not illustrated, a COG type of LDI and a COG type ofTDI 30 may be attached to one side of the display device rather than thepads. Referring to FIG. 16, the LDI and the TDI may be attached in a COGform to an area in which the pads are positioned. Therefore, a quantityof signals transferred from the outside to the display device may besignificantly reduced, a size of the flexible circuit board may bereduced, and a cost may be reduced.

That is, in the case in which a COG type of IC is used, the signalstransferred to the G/L 295 may be generated in the COG type of TDI 30and be transferred to the G/L, or may be generated in the COG type ofTDI and be connected to the G/L through the flexible circuit boardattached to a lower side of the COG type of TDI, an external buffer, andthe flexible circuit board. Alternatively, one of outputs of thealternating AC voltage may be connected to the G/L.

In first and second exemplary embodiments in which the touch sensor 10is positioned below the signal line as described above by way of examplewith reference to FIGS. 8, 10, and 11, in the case in which a person'shand touches an upper portion of the color filter of FIG. 6, the touchsensor 10 is covered by the gate line 240 or the source line 250, suchthat it is impossible to detect a touch signal. In order to overcome theproblem described above, the display device is set so that the TFTsubstrate 210 is directed toward an upward direction and the colorfilter substrate 100 is directed toward a downward direction. Therefore,the touch sensor 10 is directed toward the uppermost portion, and anyresistance material is not present on an upper surface of the touchsensor 10, such that it is possible to detect a touch by an object suchas a finger, or the like.

The display device having an embedded touch screen according to anexemplary embodiment of the present invention is characterized in thatthe touch screen is positioned on upper surfaces of the TFT and thesource lines 250 and the gate lines 240 constituting the TFT. When thetouch screen is positioned below the source lines 250 and the gate lines240, the LCD should be overturned by 180 degrees. However, it isimpossible to overturn the LCD or it is possible to mount the touchsensors on upper surfaces of the signal lines in an LCD using an IPSmode or an FFS mode corresponding to a transversal electric field modein which Vcom is not present in the color filter substrate of FIG. 5.

Before describing the technical spirit of mounting the touch sensors onthe upper surfaces of the signal lines as described above, a structureof an LCD using the transversal electric field mode will be describedbelow since the IPS mode or the FFS mode corresponding to thetransversal electric field mode in which the touch sensors according toan exemplary embodiment of the present invention will be embedded isdifferent from the TN structure.

FIG. 19 is a view illustrating a configuration of a TFT substrate amongcomponents of an LCD using a transversal electric field mode. In the LCDusing the transversal electric field mode, common electrodes 120 are notscattered over an entire surface of a color filter, but are formed inonly a partial area of a TFT substrate rather than the color filter,unlike the LCD using the TN mode described above.

As illustrated in FIG. 19, the gate lines 240 and the source lines 250are disposed in the longitudinal and transversal directions on an uppersurface of the TFT substrate, and areas formed by the gate lines 240 andsource lines 250 form pixels. TFTs 220 switching image signals areinstalled in the pixels. Gate electrodes 265 of the TFTs 220 areconnected to the gate lines 240 to receive scanning signals appliedthereto, and source electrodes 270 and drain electrodes 260 of the TFTs220 are connected to the source lines 250 and pixel electrode signallines 235, respectively. In addition, a semiconductor layer 257 of theTFT 220 forms a channel between the source electrode 270 and the drainelectrode 260 in order to apply an image signal to a liquid crystallayer. Common electrode signal lines 125 are formed in parallel with thepixel electrode signal lines 235 in the pixels as illustrated.

In the LCD having the configuration as described above, when the TFTs220 are operated to apply the image signals to the pixel electrodesignal lines 235, transversal electric fields that are substantially inparallel with each other are generated between the common electrodesignal lines 125 and the pixel electrode signal lines 235, and liquidcrystal molecules move on a plane.

Although a case in which the common electrode signal lines 125 arepositioned below the pixel electrode signal lines 235 has beenillustrated in FIG. 19, the common electrode signal lines 125 may alsobe positioned on upper pixel electrode signal lines 235 with aninsulator interposed therebetween.

FIG. 20 is a view illustrating an example of a display device having anembedded touch sensor according to an exemplary embodiment of thepresent invention using a common electrode in a transversal electricfield mode. Referring to FIG. 20, eight pixels partitioned by the gateline 240 and the source lines 250 are present, and the common electrodesignal lines 125 of four pixels are collected to form one commonelectrode partitioned by a solid line. The solid line of FIG. 20 is avirtual partition representing that the common electrode lines 125 arecollected in one common electrode 120, and in reality, only commonelectrode signal lines 125 denoted by an oblique line are present.

Four common electrode signal lines 125 are coupled and are electricallyconnected to each other between common electrode signal lines 125 ofdifferent pixel electrodes 230 as in the left of a lower commonelectrode 230 or are coupled and are electrically connected to eachother on upper surfaces or lower surfaces of the gate lines 240 and thesource lines 250 therebetween, thereby making it possible to form onecommon electrode 120.

The common electrodes 120 at which a plurality of common electrodesignal lines 246 are coupled to each other may be operated as the touchsensors according to the present invention, and the sensor signal lines22 connect the common electrodes 120 to the TDI 30.

The common electrodes 120 are also installed on upper surfaces or lowersurfaces of the gate lines 240 or the source lines 250 in order toincrease contact areas with an object such as a finger, or the like, inaddition to a general case in which they are positioned in pixel partsas illustrated in FIG. 28. According to an exemplary embodiment of thepresent invention, in the case in which the common electrodes 120 areinstalled on the upper surfaces or lower surfaces of the gate lines 240or the source lines, since parasitic capacitance is generated betweenthe common electrodes 120 and the driving signal lines (the source linesand the gate lines), it is preferable to reduce overlap areas of thecommon electrodes overlapped with the driving signal lines (the sourcelines and the gate lines).

As an method thereof, as illustrated in FIG. 29, in order to reduce theoverlap areas between the common electrodes 120 and the driving signallines (the source lines and the gate lines), one or more slits 121(portions in which grooves are cut) may be formed in some regions of thecommon electrodes 120, that is, the regions in which the driving signallines and the common electrodes overlap with each other. Therefore,according to the present invention, the common electrodes are not formedin the slits 121. The overlap areas with the driving signal lines (thesource lines and the gate lines) are reduced by the slits 121 of thecommon electrodes 120, as illustrated in FIG. 28, thereby making itpossible to reduce an occurrence of the parasitic capacitance. In thiscase, a size of connecting parts 122 connecting the respective commonelectrodes 120 to each other is not limited, and may be changeddepending on a size of the slit 121.

Referring to A and B of FIG. 20, the sensor signal lines 22 areinstalled on side surfaces of the source lines 250. However, actually,the sensor signal lines 22 are disposed on the upper surfaces or thelower surfaces of the source lines 250 so as to overlap with the signallines, such that they are not viewed with the naked eyes, and connectthe common electrodes 120 operated as the touch sensors 10 to the TDI30.

Although four common electrode signal lines 125 are disposed in onecommon electrode 120 in FIG. 20, several tens to several hundreds ofcommon electrode signal lines 125 actually form one common electrode120.

A significant number of pixels are present in the display device. Forexample, an HD display device has pixels of 1280×720, a significantnumber of common electrodes 120 according to the present inventionshould be installed in the LCD using the transversal electric fieldmode. FIG. 20 illustrates a shape in which the common electrodes 120 aredisposed in the transversal electric field mode. Referring to FIG. 20, aplurality of common electrodes 120 in the transversal electric fieldmode are installed in the longitudinal and transversal directions, andeach common electrode 120 is connected to one sensor signal line 22 tothereby be connected to the TDI 30.

The common electrode 120, which is a portion constituting the pixel,should be a transparent electrode formed of ITO. The sensor signal lines22 may be formed of the same material as the common electrodes 120, andmay be separated in a predetermined region, and one or more signal linesmay connect one touch sensor 10 and the TDI 30. In addition, when thesensor signal lines 22 connect the common electrodes 120 operated as thetouch sensors 10 and the TDI 30 to each other, the sensor signal lines22 are formed to overlap with pixel regions except for the pixel regionsincluded in the touch sensors 10, where the sensor signal lines 22 maybe formed to be (vertically or horizontally) overlapped with one or moresub-pixel regions or overlap with some regions of one sub-pixel.

For example, as illustrated in (a) of FIG. 30, in the case in which onepixel includes a red (R) sub-pixel, a green (G) sub-pixel, and a blue(B) sub-pixel, the sensor signal lines 22 may be formed to (verticallyor horizontally) overlap with the respective R, G, and B sub-pixels byconnecting three sensor signal lines 22 to the common electrodes 120operated as one touch sensor 10, where the respective sensor signallines 22 may be formed to be overlapped between boundary lines of the R,G, and B sub-pixels, or may be formed to overlap with the boundary linesof the R, G, and B sub-pixels.

In addition, as illustrated in (b) of FIG. 30, a first sensor signalline 22-1 connected to a first touch sensor 10-1 positioned at theuppermost portion in one column is formed to overlap with a regionbetween a line on which the B sub-pixel is disposed and a line on whichthe G sub-pixel is disposed, or is formed to overlap with some regionsof a boundary line between the B sub-pixel and the G sub-pixel. Inaddition, a second sensor signal line 22-2 connected to a second touchsensor 10-2 positioned below the first touch sensor 10-1 is formed tooverlap with a region between the line on which the G sub-pixel isdisposed and a line on which the R sub-pixel is disposed, or is formedto overlap with a boundary line region between the G sub-pixel and the Rsub-pixel. In addition, a third sensor signal line 22-3 connected to athird touch sensor 10-3 positioned below the second touch sensor 10-2 isformed to overlap with a region between the line on which the Rsub-pixel is disposed and a line on which the B sub-pixel of a leftpixel is disposed, or is formed to overlap with a boundary line regionbetween the R sub-pixel and the B sub-pixel of the left pixel.

However, the sensor signal lines 22 are not limited to theabove-mentioned illustration, and a width thereof may be variouslyformed in a region over the sub-pixel. As such, the sensor signal lines22 according to an exemplary embodiment of the present invention areformed to overlap with the pixel regions except for the regions of thecommon electrodes 120 formed as the touch sensors 10, such that thewidth of the sensor signal lines 22 is sufficiently secured, therebymaking it possible to decrease a resistance value of the sensor signallines 22, and to stably apply a common voltage to the regions other thanthe touch sensors 10 at the time of driving the display device. Inaddition, in the case in which the sensor signal lines 22 are formed ofthe same material as the common electrodes 120, since the touch sensors10 and the sensor signal lines 22 may be formed by one mask, costs formanufacturing the display device may also be reduced.

Although the exemplary embodiment of the present invention illustratesthe case in which the common electrodes 120 operated as the touchsensors 10 are indicated by a quadrangular shape, the common electrodes120 are not limited thereto, but may be implemented in various shapessuch as triangular shape, a pentagonal shape, and the like, and edges ofthe common electrodes operated as the touch sensors 10 or the sensorsignal lines 22 may be configured in a zigzag shape having apredetermined angle in order to improve visibility. In addition, apattern of a clamp (>) shape or a fine pattern of various shapes isformed in the common electrodes operated as the touch sensors 10 or thesensor signal lines 22.

As another example, in the case in which the sensor signal lines 22connected to the common electrodes 120 are installed above or below thegate lines 240 or the source lines 250, the sensor signal lines 22 donot need to be transparent electrodes. When the sensor signal lines 22connected to the common electrodes 120 are formed of a metal such ascopper, aluminum, or the like, they have a resistance lower than that ofthe transparent electrode, which is advantageous in capturing a touchsignal.

The sensor signal lines 22 may be patterned and manufactured using aseparate dedicated mask. When the sensor signal lines 22 aremanufactured commonly using a source metal, a gate metal, or a metalmask in a process of manufacturing the TFT, the number of masks isreduced, thereby making it possible to reduce a manufacturing cost. Whenthe common electrodes 120 and the common electrode lines 125 of FIG. 20are installed to overlap with the source lines 250 or the gate lines240, the common electrodes 120 and the common electrode lines 125 areaffected by a pixel signal voltage or gate on/off voltage applied to thesource lines 250 or the gate lines 240, and the above effect acts asnoise at the time of detecting the touch. In order to avoid theabove-mentioned problem, two methods are suggested.

A first method is a method for detecting a touch using a poach period inwhich the LCD is not driven. The poach period includes a poach of a linesynchronization signal Hsync and a poach of a frame synchronizationsignal Vsync, and since a signal voltage for configuring the image ofthe LCD is not changed in the poach, the TDI receives the framesynchronization signal, the line synchronization signal, or informationrelated to data enable or poach from the LDI or the ICON, thereby makingit possible to detect the touch signal using the poach.

A second method is a method for installing the G/L (not shown) betweenthe gate lines 240 or the source lines 250 and the common electrodes120. The G/L used therein uses the same technical spirit as the G/Ldescribed above. According to the present invention, in the displaydevice using the common electrodes as the touch sensors, a method forapplying the driving signal to the G/L includes 1) a method for applyinga DC voltage or an alternating voltage output from a TDI, and 2) amethod for applying the same alternating voltage as the AC voltageapplied to the TDI from a power management IC (PMIC), in the samecontents as the G/L described above.

FIG. 21 illustrates a method for detecting a touch using a commonelectrode of the display device having an embedded touch screenaccording to an exemplary embodiment of the present invention thattogether performs a function of a touch sensor as the common electrode.In a touch sensor structure according to an exemplary embodiment formedin the matrix structure as illustrated in FIG. 9, there are touchsensors performing a touch signal detection and touch sensors that donot perform the touch signal detection, where the touch sensorsperforming the touch signal detection are referred to as sensing pads(SP) and the touch sensors that do not perform the touch signaldetection are referred to as non-sensing pads (NSP). Referring to FIG.21, the touch sensors connected to the touch signal detecting unit areSP, and touch sensors which are not connected to the touch signaldetecting unit are NSP. Although FIG. 21 illustrates only one SP by wayof example, a plurality of touch sensors may be operated as the sensingpads (SP) through a plurality of touch signal detecting units, therebymaking it possible to reduce a time taken to detect the touch signal.

Referring to FIG. 9, all touch sensors belonging to one transversaldirection such as Row1 or Row2 may be operated as SP. Alternatively, alltouch sensors belonging to one longitudinal direction such as Col1 orCol2 may be operated as SP. However, when the touch signals aresimultaneously detected using the touch sensors in the longitudinaldirection, the SPs are affected by each other due to parasiticcapacitance between a signal line and a signal line, which may causeerror of the detection signal.

However, as described above, even in the structure as illustrated inFIG. 9, when the AC input power is used, the interference due to theparasitic capacitance between the signal line and the signal line isremoved, thereby making it possible to detect the touch signal.

In addition, in the case in which the touch signal is detected onlyusing the AC input power and the alternating voltage necessary for thetouch detection within the TDI is not used, it is also possible to usethe sensing pads (SP) which may perform the touch detection in all touchsensors of FIG. 9. In this case, since a plurality of touch signaldetecting units, an ADC, and a DAC are required, a volume of the TDI maybe increased, but there is an advantage that the touch signal may bedetected within a fast time.

Again referring to FIGS. 9 and 19, when the touch signal is detectedusing the touch sensors 10 included in one longitudinal direction or onetransversal direction, in the case in which the volume of the TDI isincreased due to an increase in the number of the touch signal detectingunits 14, it is also possible to detect the touch signal by dividing thenumber of the touch sensors. For example, in the case in which the touchsignal is detected using five touch sensors in a Row1 direction, thetouch signal is first detected using even-numbered touch sensors, thatis, touch sensors of (Row1, Col2) and (Row1, Col4) as the sensing pads,and the touch signal is then detected from odd-numbered touch sensors((Row1, Col1), (Row1, Col3) and (Row1, Col5)). If there are a pluralityof touch sensors, it is also possible to divide the number of the touchsensors three times or four times.

The above-mentioned method has an advantage that a small number of touchdetecting units 14 operate the plurality of touch sensors 10 to detectthe touch signal, thereby making it possible to reduce the volume of theTDI.

For example, in the case in which the number of touch sensors installedin Row1 is 30, when 15 touch signal detecting units are used, and theeven-numbered and odd-numbered touch sensors are connected to the touchdetecting units by classifying a time difference, it is possible todetect the touch signal from the 30 touch sensors using 15 touch signaldetecting units.

Although the example in which the touch sensors including theeven-numbered touch sensors and the odd-numbered touch sensors areclassified to be connected to the touch signal detecting units isillustrated, it is also possible to divide the touch sensors into a leftdirection and a right direction to perform a time sharing to beconnected to the touch signal detecting units.

As such, according to the present invention, it is possible to dividethe touch sensors into plural and to share the touch signal detectingunit using a time sharing method. In this case, it is possible topartition the touch sensors into an even-number or an odd-number, orclassify the touch sensors into the left direction and the rightdirection. Besides, it is possible to partition the touch sensors into aplurality of n touch sensors according to any defined rule.

As described above, according to the present invention, in the methodfor detecting the touch signal using the common electrodes, an object ofthe common electrodes substantially serves as the common electrodes ofthe display device, the common electrodes in the transversal electricfield mode of the LCD, or the cathode of the OLED, particularly, theAMOLED.

Therefore, a common voltage needs to be always applied to the commonelectrodes, and a driving method in which the common voltage is changedshould not be applied. The above-mentioned driving method will bedescribed below, but a method for applying a constant common voltage tothe common electrodes is as follows.

Referring to FIG. 21, the SP and the NSP co-exist in the commonelectrodes. The method for applying the unchanged common voltage to thecommon electrodes includes first applying a common voltage Vcom, whichis a DC voltage having constant magnitude, including 0V or a ground tothe NSP, and not changing the common voltage Vcom even in the case inwhich the touch signal is detected from the SP. To this end, when thetouch signal is detected from the SP, the common voltage Vcom connectedto the NSP maintains the constant voltage.

In addition, the common voltage having the same magnitude may be appliedto all NSPs, the common voltage may be differentially supplied for eachof individuals, for each of groups, and for each of positions.

In addition, the SP is also precharged with the common voltage Vcom.When the touch is detected from the SP, a slight potential variationoccurs in the SP, such that a slight variation occurs in the commonvoltage Vcom applied to the SP, which causes abnormality of quality ofimage, but since the object such as the finger, or the like is incontact with the screen, the abnormality of quality of image of thescreen will not be viewed.

As such, according to the present invention, it is possible to alwaysapply the common voltage required for the display device to the commonelectrodes operated as the NSP, and to normally drive the display deviceusing the common voltage required for the display device as theprecharge voltage for the common electrodes operated as the SP.

In addition, the common voltage applied to the NSP and the commonvoltage precharged to the SP are the same voltage. Alternatively, thecommon voltage applied to the SP may be greater or smaller than thecommon voltage applied to the NSP. When the precharge is intended to beperformed within a fast time due to turn on resistance of a switchingelement to which the common voltage is transferred to the SP through anon/off switching element at the common voltage or the parasiticcapacitance connected to the SP, the case in which the charging fallsshort due to a lack of a charging time may occur.

The common voltage is a positive voltage including the ground, but sincea negative voltage may be applied, it is preferable that when the commonvoltage is the positive voltage, the common voltage higher than a targetvalue is applied, and when the common voltage has a negative value, thecommon voltage lower than the target value is applied.

According to the present invention, when the common voltage is appliedto the common electrodes, a means for varying magnitude of the commonvoltage is included, the means for varying the common voltage may beimplemented inside or outside the TDI. In the case in which the meansfor varying the common voltage is implemented in the TDI, the commonvoltage may be generated in a combination of the DAC or internalresistance in the TDI, and magnitude of the generated common voltage maybe adjusted through a resistor. Although not shown, a plurality ofresistors are matched in a one-to-one scheme for each of magnitudes ofthe common voltage, and it is possible to select different commonvoltage according to a selection of the resistor. For example, eightdifferent common voltages may be mapped to a resistor block including 3bits, and when 00h, which is the least significant bit (LSB), isselected, the magnitude of the common voltage is −1.5V, 01h is −1.6V,and the magnitude of the last 07h is −22V. In addition, in the case inwhich the means for varying the common voltage is implemented outsidethe TDI, the voltage may be directly applied to the common electrodesfrom the outside, or the voltage may be applied by varying the magnitudeof the common voltage by an external variable resistance, and in thiscase, it is preferable that the TDI further includes a means capable ofselecting the application of the common voltage generated from theoutside.

In the present invention, a power supply unit required by the TDI andthe LDI when the LDI and the TDI are integrated into one IC is generatedby a common power supply unit, and in this case, the TDI generates thecommon voltage, and the meaning that the magnitude of the common voltageis adjusted is the same meaning that one IC in which the TDI and the LDIare integrated performs the adjustment of the magnitude of the commonvoltage.

In addition, the above-mentioned common voltage is generated from aseparate power management IC (PMIC) generating the AC input power, andthe PMIC has a means for changing the magnitude of the common voltage.The PMIC has a means for alternating the AC voltage in synchronizationwith a control signal of the LDI or the TDI. For example, when thecontrol signal output from the TDI is low, the PMIC may alternatingVc21, which is the AC voltage, from 10V, which is high, to 3V, on thebasis of the earth ground, and when the control signal output from thePMIC is high (Hi), Vc21 may be swung from 3V to 10V. Of course, Vc22 mayalways maintain a constant DC voltage in synchronization with Vc21.

In a method for detecting a touch of a display device having an embeddedtouch sensor utilizing the common electrodes as the touch sensoraccording to an exemplary embodiment of the present invention, since thecommon electrodes connected to the SP or the NSP should not be changed,as in a method to be described below, a method for detecting a touchsignal using the alternating driving voltage for the NSP, or a methodfor detecting a touch signal by applying the alternating driving voltageCdrv in the TDI connected to the SP may be used.

In order to solve the above-mentioned problem, the present inventionuses a method for detecting a touch signal using AC input power inaddition to the method for detecting a touch signal using the commonelectrodes.

As described below, the TDI and the LDI may be integrated into one IC tobe manufactured. In this case, as illustrated in FIG. 12, the AC poweris not applied to the TDI and the LDI, respectively, but the AC inputpower will be applied to one integrated IC.

Referring to FIG. 21, FIG. 21 illustrates some function blocks of theTDI, which are illustrated in more detail in FIG. 9. Since the methodfor detecting a touch using the common electrodes according to anexemplary embodiment of the present invention uses the touch sensorsembedded in the display device, in the case in which the TDI and the LDIuse the common ground, the common voltage applied to the commonelectrodes, which are the touch sensors of the TDI may be operated asthe common electrodes of the display device.

Therefore, the AC input power commonly having the ground is applied tothe TDI, the LDI, or the common IC in which the TDI and the LDI areintegrated, and the ground of the AC input power is Vc22. In the case inwhich it is assumed that Vcom is −2.2V on the basis of Vc22, which isthe ground of the TDI or the LDI, when Vc22 is 10V on the basis of theearth ground, which is the absolute potential, Vcom is 7.8V on the basisof the earth ground.

Referring to FIGS. 9 and 21, since the ground of the TDI is Vc22, whenthe touch sensors which are the common electrodes operated as the SP arepositioned in the display device, the parasitic capacitance occursbetween the gate line 240 and the source lines 250 over or below thetouch sensors, or when the G/L 295 exists between the touch sensors 10and the driving signal lines, the parasitic capacitance also occursbetween the touch sensors 10 and the G/L 295. In this case, theparasitic capacitance is modeled into Cvcom, when Cvcom overlaps withthe signal line, VVcc is a potential of the signal line, and when Cvcomoverlaps with the G/L, the potential of the G/L is VVcc. In addition,the parasitic capacitance also occurs between the NSP and the SP, whichis represented by Cp, and since the potential of the NSP is Vcom, aground of the Cp is Vcom.

In this structure, it is possible to detect the touch signal insynchronization with the rising edge or a falling edge of thealternating voltage when the AC input voltage is swung, and in thiscase, a detected signal is represented by the following Equation.

$\begin{matrix}{{D\text{/}B} = {{Vpre} \pm {{Vswing}\frac{Ct}{{Cvcom} + {Cp} + {Ct}}}}} & \left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack\end{matrix}$

Here, Ct is touch capacitance generated between the SP and the finger,and Vswing is magnitude of the alternating voltage that the AC inputvoltage having Vc22 as the ground is swung on the basis of the earthground. Vpre is a voltage charged in the SP, which is Vcom. In addition,a positive or negative polarity after Vpre is interworked with therising or the falling of the alternating voltage, the polarity when thealternating voltage falls is negative, and the polarity when thealternating voltage rises is positive. The above-mentioned rule isapplied to the overall of the present specification.

The TDI calculates a change of magnitude of the voltage when Ct is addedon the basis of when Ct does not exist in Equation 5 to calculatemagnitude of Ct, thereby making it possible to confirm whether or notthe touch is performed and to calculate a touched area.

When the touch signal is detected in synchronization with the risingedge or the falling edge of the alternating AC input voltage, some timeis required until the touch signal is stabilized after the rising edgeor the falling edge. This time may adjust a delay detection time by asetting means included in the TDI, for example, the setting of theresistor in the TDI.

FIG. 17 illustrates a display device having an embedded touch screenaccording to a third exemplary embodiment of the present invention. InFIG. 17, the touch sensors 10 are positioned on upper surfaces of thegate lines 240 and the source lines 250, and have a mesh structure asillustrated in FIG. 10. In an exemplary embodiment having thisstructure, the touch sensors 10 may be used in a transverse electricfield mode such as an IPS mode, or the like, in which the commonelectrode of FIG. 6 is not present, or may be used in a state in whichVcom present in an area of the BM 130 between the RGB color filters 110is removed by etching. However, connection points between the commonelectrodes 120 should remain in order to interconnect the commonelectrodes 120. The touch sensors 10 include the common electrodes 120of FIG. 20.

The touch sensors 10 are installed above the gate lines 240 and thesource lines 250, and are disposed at a width wider than those of thegate lines 240 and the source lines 250. In addition, the touch sensors10 are formed in the mesh structure as illustrated in FIG. 10 or areformed in the matrix structure as illustrated in FIG. 9. In addition, inthe case in which the touch sensors 10 are formed in the matrixstructure as illustrated in FIG. 9, the touch sensors 10 may also beformed in a structure that is not the mesh structure, but may be formedin the mesh structure. As another example, in the case in which thetouch sensors 10 are formed in the matrix structure, the touch sensors10 are may be formed in a mixture structure of the mesh structure and anon-mesh structure. That is, some of the touch sensors 10 may not beformed in the mesh structure, and the other of the touch sensors 10 maybe formed in the mesh structure. In addition, in the case in which thetouch sensors 10 are formed in the matrix structure, it is preferablethat the touch sensors 10 have areas that become small as they becomeclose to the TDI 30.

In addition, it is preferable that the touch sensors 10 are disposed atpositions adjacent to the pixel electrodes 230, are disposed so as notto overlap with the pixel electrodes 230 in the vertical direction, andare installed in the sub-pixel unit.

In addition, the number of sensor signal lines 22 connected to the touchsensors 10 is one or plural, and in the case in which the number ofsensor signal lines 22 is plural, the sensor signal lines are bonded toeach other in the A/A or are bonded to each other in the non A/A inwhich the TDI 30 is disposed.

In addition, the sensor signal lines 22 are installed above the gatelines 240 and the source lines 250, and include transparent wiringsformed of at least one transparent conductive material such as indiumtin oxide (ITO), antimony tin oxide (ATO), carbon nano tube (CNT),indium zinc oxide (IZO), nano wire, silver nano wire, or the like, andmetal wirings formed of a metal. Here, it is preferable that thetransparent wirings are formed in the A/A of the display device and thetransparent wirings or the metal wirings are formed in the non A/A ofthe display device. Alternatively, the sensor signal lines 22 are notinstalled above the gate lines 240 and the source lines 250, but may beinstalled over the entire area of the display device, such as a pixelarea of the display device.

In the case in which the touch sensors 10 are positioned on the uppersurfaces of the gate lines 240 and the source lines 250 as describedabove, the BM 130 of the color filters 110 visually blocks the touchsensors 10 when the color filters 110 are coupled to the TFT substrate210. Therefore, even though a metal is used as a material of the touchsensors 10, a flash phenomenon of the metal is not generated.Accordingly, the metal such as copper, aluminum, or the like, may beused as the material of the touch sensors 10, such that a resistance isreduced, thereby making it possible to more rapidly detect a touchsignal and reduce a consumed current.

A protection layer may be added on upper surfaces of the touch sensorsof FIG. 17, if necessary.

In a third exemplary embodiment of the present invention, the touchsensors 10 are applied with the alternating driving voltage generatedfrom the TDI 30 or the AC alternating voltage generated from the PMIC,and the touch detecting unit 14 detects the touch signals insynchronization with a rising or falling edge of the AC alternatingvoltage.

In the display device having an embedded touch screen according to athird exemplary embodiment of the present invention, the touch sensors10 positioned on the upper surfaces of the gate lines 240 and the sourcelines 250 malfunction by changes in voltages of the gate lines 240 andthe source lines 250, and a display device having an embedded touchscreen according to a fourth exemplary embodiment of the presentinvention further including a G/L 295 is suggested in order to solvethis problem.

FIG. 18 is a view illustrating a display device having an embedded touchscreen according to a fourth exemplary embodiment of the presentinvention. When the touch sensors 10 are positioned in any area of theactive area of the display device or on upper surfaces of the gate lines240 and the source lines 250, a G/L 295 is installed between the touchsensors 10 and the gate and source lines 240 and 250. Although anexample in which the touch sensors 10 are installed on the uppersurfaces of the gate lines 240 and the source lines 250 has beenillustrated in FIG. 18, the touch sensors 10 may be disposed on anypositions such as the gate lines 240, the source lines 250, and thelike, except for upper surfaces of driving signal lines of the displaydevice. In addition, this display device includes an AMOLED, a PMOLED,or the like, as well as an LCD.

Referring to FIG. 18, the touch sensors 10 are positioned on uppersurfaces of TFTs constituting the display device, the first insulator285 is positioned below the touch sensors 10, and the G/L 295 ispositioned below the first insulator. It is preferable that the firstinsulator 285 is applied over the entire active area (A/A) of thedisplay device.

The G/L 295 or the touch sensors 10 are positioned on the upper surfacesof the gate lines 240 and the source lines 250 or in any area of the A/Aof the display device, are formed in the mesh structure as illustratedin FIG. 5 or is formed in a non-mesh structure as illustrated in FIG. 4,and a DC or alternating driving voltage is applied to the G/L 295.

All of the features of the present invention are similarly applied tothe case in which the touch sensors 10 are positioned above the gatelines 240 and the source lines 250, similar to the display deviceshaving an embedded touch screen according to the first and secondexemplary embodiments corresponding to the case in which the touchsensors 10 are positioned below the signal lines.

After the touch sensors 10 are formed on the uppermost surface of FIG.18, a second insulator 286 is not applied, which accomplishes a costreducing effect. However, the second insulator 286 may be installed onupper surfaces of the touch sensors 10, if necessary.

In a fourth exemplary embodiment of the present invention, a method forapplying the driving signal to the G/L 295 includes 1) a method forapplying a DC voltage or an alternating voltage output from a TDI, and2) a method for applying the same alternating voltage as the AC voltageapplied to the TDI from a power management IC (PMIC), similar to thecontents applied to the second exemplary embodiment.

In addition, it is preferable that the display device having an embeddedtouch screen according to a fourth exemplary embodiment of the presentinvention further includes a buffer or an operational amplifier (OPAMP)amplifying the driving signals of the TDI transferred to the G/L 295,similar to the display device having an embedded touch screen accordingto the second exemplary embodiment.

Further, in a fourth exemplary embodiment of the present invention, thetouch sensors 10 are applied with the alternating driving voltagegenerated from the TDI 30 or the AC alternating voltage generated fromthe PMIC, and the touch detecting unit 14 detects the touch signals insynchronization with a rising or falling edge of the AC alternatingvoltage.

In addition, the same voltage as the AC alternating voltage synchronizedat the time of detecting the touch signal by the touch detecting unit 14is applied to the G/L.

The touch sensors 10 applied to the first to fourth exemplaryembodiments of the present invention are formed in the mesh structure asillustrated in FIG. 10 or are formed in the matrix structure asillustrated in FIG. 9. In addition, in the case in which the touchsensors 10 are formed in the matrix structure as illustrated in FIG. 9,the touch sensors 10 may also be formed in a structure without havingthe mesh structure, but may be formed in the mesh structure. As anotherexample, in the case in which the touch sensors 10 are formed in thematrix structure, the touch sensors 10 are may be formed in a mixturestructure of the mesh structure and a non-mesh structure. That is, someof the touch sensors 10 may not be formed in the mesh structure, and theother of the touch sensors 10 may be formed in the mesh structure. Inaddition, in the case in which the touch sensors 10 are formed in thematrix structure, it is preferable that the touch sensors 10 have areasthat become small as they become close to the TDI 30.

Meanwhile, in the case in which the size of the touch sensor accordingto the exemplary embodiment of the present is greater than the objectsuch as the finger or the pen, it is impossible to accurately detect thetouch position. Referring to FIG. 22, in the case in which the objectsuch as the finger or the pen is moved in a vertical direction or ahorizontal direction, it is impossible to calculate a touch coordinatewhen the object is moved within one touch sensor 10. In order tocalculate the touch coordinate, area changes of two or more touchsensors need to occur.

A method for solving the above-mentioned problem includes sharing atouch sensor area in a longitudinal direction or a transversal directionby crossing two touch sensors. FIGS. 23A and 23B illustrate examplesabout a sharing of a touch sensor area according to an exemplaryembodiment of the present invention, where the area is shared in alongitudinal direction. In FIGS. 23A and 23B, four touch sensors 10formed in a quadrangular shape are present, and the respective touchsensors 10 share 50% up to the central portion of the touch sensors 10adjacent to each other, that is, in a length direction. For example, asecond sensor is changed to a triangle having a circular pattern, andshares an area between a first sensor and a third sensor by expandingown area as much as a length of 50% in the first and third sensors, thatis, a length of the central portion of the touch sensors.

Therefore, a situation in which it is impossible to calculate a touchcoordinate because an object moves only in one touch sensor even in thecase in which the object vertically moves in one touch sensor in FIG. 22so as not to cause the change of the area is changed to a situation inwhich it is possible to detect the touch because a change of the area inthe two touch sensors occurs.

FIG. 23A illustrates a case in which a contact area is one when thetouch sensors vertically contacts with each other, and in this case, avertical displacement of a very small object may not be detected. Inorder to solve the above-mentioned problem, as illustrated in FIG. 23B,when the contact area of the touch sensors which are verticallypositioned is increased to plural (e.g., three in the example), that is,the number of vertexes which vertically overlap with each other isincreased, the area sharing between the touch sensors closely occurs,thereby making it possible to easily detect a change of the objecthaving a small area.

In this case, the number of vertexes overlapping with each othernecessarily includes a half vertex such as 1.5, or 2.5, or 3.5, so thecontact areas overlapped between the objects are the same as each other,such that the parasitic capacitance generated between the touch sensorsis equal to each of the touch sensors. A concept of the half vertex wasused in an aspect in which an area of a right triangle of an upper endtouch sensor sharing the area in a zigzag is just 50% of an area of aneighboring triangle thereof, and an area of a left triangle of a lowerside touch sensor is also just 50% of an area of a neighboring trianglethereof, with reference to FIG. 23B.

In addition, one sensor simultaneously shares the area in an upper sideand a lower side facing each other, and a length of the area sharing isminimum 0% (not share the area) to maximum 50%.

FIG. 24 illustrates an example in which the touch sensors in thetransversal direction share the area. Similar to the example in thelongitudinal direction, the touch sensors which are left and right inthe transversal direction share the area, and share the area as much asa length of 0 to 50%. The overlapping vertexes preferably include thehalf vertex such as 2.5 or 3.5. Although not illustrated, the signallines disposed in a vertical direction also have a zigzag shape.

FIG. 25 is a view of an example in which up and down or left and rightareas of the touch sensors are shared in a case in which the touchsensors are positioned on upper surfaces or lower surfaces of gate linesor source lines according to an exemplary embodiment of the presentinvention. Referring to FIG. 25, an upper side touch sensor and a lowerside touch sensor share the area, an interval between the touch sensorsat the time of sharing the area is illustrated. A lattice of FIG. 25indicates a pixel of the display device, solid lines in the longitudinaldirection are the gate lines 240, and solid lines in the transversaldirection is the source lines 250.

As such, when the touch sensors are present on the upper surfaces or thelower surfaces of the signal lines, the touch sensors share the area ina step shape in a unit of pixel. This is also equally applied to thearea sharing of the sensors disposed in the transversal direction or thearea sharing of the sensors disposed in the longitudinal direction.

The interval between the sensors is at least one pixel or more. If thecommon electrodes serving as the touch sensors in the unit of pixelshare the area as in FIG. 23 or 24 in an exemplary embodiment of thepresent invention sharing the touch sensors with the common electrodes,the pixels to which the common electrodes are not applied occur, therebycausing defect of quality of image.

FIG. 26 illustrates an example of a sharing of a touch sensor area in acase in which the common electrodes act as the touch sensors. Referringto FIG. 26, the source lines 250 in the longitudinal direction and thegate lines 240 in the transversal direction are present, and the areasharing occurs at the driving signal lines as a boundary. That is, inthe case in which the common electrodes act as the touch sensors,different touch sensors 10 c and 10 d are divided at the source lines250 or the gate lines 250 as the boundary in order to prevent asituation in which the common electrodes are not applied to separatepixels.

Alternatively, in the case in which process capability of an equipmentin a process of manufacturing the LCD is good, different touch sensorsmay be divided from the upper surfaces or the lower surfaces of thesignal lines.

In the display device including the touch screen according to anexemplary embodiment of the present invention, the LCD driving IC (LDI)and a touch driving IC (TDI) should be used. The LDI and the TDI aredivided to be separately used as illustrated in FIG. 12, but in thiscase, a process of manufacturing the LDI and the TDI is added, therebyincreasing production costs. In addition, when the IC is disposed at oneside of the display device in FIG. 16, a space may be increased. Inorder to solve the above-mentioned problems, the present inventionsuggests a method in which two ICs are integrated into one IC.

FIG. 27 illustrates a structure of an IC in which an LDI and a TDI areintegrated into one according to an exemplary embodiment of the presentinvention. Referring to FIG. 27, an area 1 and an area 3 are the TDI, inwhich the components of FIG. 9 are divided to be distributed, or areincluded in the area 1 and the area 3, respectively. Alternatively, anarea 2 is the TDI, and the components of the TDI of FIG. 9 are allincluded in the area 2.

In addition, the area 2 is an LDI area. The LDI may be positioned at thecentral portion of the integrated IC, or may be disposed at the positionof the area 1 or the area 3.

As such, if the TDI and the LDI are integrated into one IC, the powergenerated from the TDI or the LDI may be shared, and since one of thepower of the LDI and the power of the TDI may be deleted, an area of theIC is decreased, thereby reducing the costs.

In this case, since the signal needs not to be transmitted between theTDI and the LDI, the TDI and the LDI need not to be connected to eachother through the signal in the IC, but the TDI and the LDI may sharethe necessary signal in the IC, if necessary.

In the display device having an embedded touch screen according to anexemplary embodiment of the present invention, the touch sensor and thesensor signal line are formed to be positioned on the same line as thedriving signal line such as the source line, the gate line, or the like,of the display device, to prevent the touch sensor and the sensor signalline from being observed in the display device and remove an influenceof the touch sensor and the sensor signal line on the display device.

In addition, a recognition error of the touch signal due todisconnection of the sensor signal line may be prevented, such thattouch recognition performance of the touch device may be stablymaintained.

Further, the guard layer (G/L) is installed to reduce the parasiticcapacitance generated between the touch sensor and the sensor signalline and components of the display device, thereby easily obtaining thetouch signal.

Further, the touch sensitivity may be improved by applying a method forapplying a DC voltage or an alternating voltage output from a TDI and amethod for applying the same alternating voltage as an AC voltageapplied to the TDI from a power management IC (PMIC), respectively, to aguard layer.

Further, the sensor signal line is used together with the source metaland the gate metal used in the display device in an area except for theactive area (A/A) of the display device to reduce a resistance of thesensor signal line, thereby easily detecting the obtained touch signal.

It will be obvious to those skilled in the art to which the presentinvention pertains that the present invention is not limited to theabove-mentioned exemplary embodiments and the accompanying drawings, butmay be variously substituted, modified, and altered without departingfrom the scope and spirit of the present invention.

What is claimed is:
 1. A display device having an embedded touch screen,the display device comprising: a substrate on which pixel electrodes anddriving signal lines are disposed, wherein a sensor layer on which touchsensors and sensor signal lines are disposed is formed above or belowthe driving signal lines, and a guard layer configured to preventinterference of signals between the driving signal lines and the sensorlayer, wherein the guard layer is formed between the driving signallines and the sensor layer, and applied with a first voltage and asecond voltage which are different from each other.
 2. The displaydevice of claim 1, wherein the guard layer is divided to be overlappedwith the touch sensors in a one-to-one scheme.
 3. The display device ofclaim 2, wherein the guard layer overlapped with a first touch sensordetecting a touch is applied with the first voltage applied to the firsttouch sensor, and the guard layer overlapped with a second touch sensorthat does not detect the touch is applied with the second voltageapplied to the second touch sensor.
 4. The display device of claim 1,wherein the first voltage is an alternating voltage applied to a firsttouch sensor detecting a touch.
 5. The display device of claim 1,wherein the first voltage is a precharge voltage applied to a firsttouch sensor detecting a touch.
 6. The display device of claim 1,wherein the second voltage is a direct current (DC) voltage or a groundvoltage applied to a second touch sensor that does not detect a touch.7. The display device of claim 1, wherein the first voltage and thesecond voltage are supplied from a touch drive IC.
 8. The display deviceof claim 7, wherein the touch drive IC is integrated with a displaydrive IC.
 9. The display device of claim 7, wherein the touch drive ICdetects a touch based on an alternating voltage, which is the firstvoltage.
 10. The display device of claim 1, wherein the first voltageand the second voltage are supplied from a power management IC.
 11. Amethod for detecting a touch of a display device having an embeddedtouch screen including a substrate on which pixel electrodes and drivingsignal lines are disposed, the method comprising: forming a sensor layeron which touch sensors and sensor signal lines are disposed, above orbelow the driving signal lines, forming a guard layer between thedriving signal lines and the sensor layer, and applying the guard layerwith a first voltage and a second voltage which are different from eachother.
 12. The method of claim 11, wherein the guard layer is divided tobe overlapped with the touch sensors in a one-to-one scheme.
 13. Themethod of claim 12, wherein in the applying the guard layer with thefirst voltage and the second voltage, the guard layer overlapped with afirst touch sensor detecting a touch is applied with the first voltageapplied to the first touch sensor, and the guard layer overlapped with asecond touch sensor that does not detect the touch is applied with thesecond voltage applied to the second touch sensor.
 14. The method ofclaim 11, wherein the first voltage is an alternating voltage applied toa first touch sensor detecting a touch.
 15. The method of claim 11,wherein the first voltage is a precharge voltage applied to a firsttouch sensor detecting a touch.
 16. The method of claim 11, wherein thesecond voltage is a direct current (DC) voltage or a ground voltageapplied to a second touch sensor that does not detect a touch.
 17. Themethod of claim 11, wherein the first voltage and the second voltage aresupplied from a touch drive IC.
 18. The method of claim 17, wherein thetouch drive IC is integrated with a display drive IC.
 19. The method ofclaim 17, wherein the touch drive IC detects a touch based on analternating voltage, which is the first voltage.
 20. The method of claim11, wherein the first voltage and the second voltage are supplied from apower management IC.